Display device and manufacturing method thereof

ABSTRACT

A display device with improved reliability and a manufacturing method of the same with improved yield. A display device according to the invention comprises a display area including a first electrode, an insulating layer covering an edge of the first electrode, a layer containing an organic compound, which is formed on the first electrode, and a second electrode. The first electrode and the insulating layer are doped with an impurity element of one conductivity.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a display device that comprises anelement including a light emitting material sandwiched betweenelectrodes (hereinafter referred to as a light emitting element), and toa manufacturing method of the display device. In particular, theinvention relates to a display device using a light emitting materialthat generates EL (Electro Luminescence) (hereinafter referred to as anEL material).

2. Description of the Related Art

In recent years, an EL display device utilizing electro luminescence(hereinafter referred to as EL) has been developed. The EL displaydevice, as well as a liquid crystal display device that has been inpractical use, comprises pixels arranged in matrix to display images.Known as a driving method of pixels are a passive matrix method and anactive matrix method using transistors. In either case, what attractsattention is that self-luminous type pixels each including an EL elementformed of an EL material provide wide viewing angle and high contrast.

It is said that an EL element emits light through the followingmechanism: a voltage is applied between a pair of electrodes thatsandwich an organic compound layer, electrons injected from the cathodeand holes injected from the anode are re-combined at the luminescentcenter of the organic compound layer to form molecular excitons, and themolecular excitons return to a ground state while releasing energy tocause the EL element to emit light. Excitation state includes a singletexciton and a triplet exciton, and it is considered that luminescencecan be made through either excitation state.

However, an EL material (particularly, an organic EL material) thatmainly constitutes an EL element is characterized in that it issensitive to moisture and degrades easily. Therefore, a sealingtechnology is an essential part of manufacturing of an EL displaydevice. Known as a sealing structure is the one in which a sealingmember is provided so as to surround a display area including ELelements and a sealing substrate is formed with the sealing memberinterposed therebetween (for example, see Patent Document 1).

[Patent Document 1] Japanese Patent Laid-Open No. 2003-255845

SUMMARY OF THE INVENTION

Although the sealing structure allows a display area including ELelements to be sealed and prevents moisture from entering externally, itis not possible to inhibit completely degradation of an EL displaydevice. That is, there may occur a punctate non-light emitting area(including an area in which luminance is lowered partially) in pixels, adefect due to enlargement of the area (hereinafter referred to as a darkspot), and a defect in which a non-light emitting area at the peripheryof pixels is enlarged with time (hereinafter referred to as a shrink).

In view of the foregoing problems, the invention provides a displaydevice that can prevent degradation of an EL material and amanufacturing method of the display device.

According to the invention, an interlayer insulating film provided forplanarization is required to have high heat resistance, high insulationproperties, and a high planarization rate. Therefore, a heat resistantplanarized film is preferably used. Such an interlayer insulating filmis preferably formed by an application method typified by a spin coatingmethod instead of a CVD method or a vapor deposition method.

Specifically, it is desirable to use a heat resistant planarized filmformed by an application method as an interlayer insulating film and aninsulating layer (bank). The interlayer insulating film and theinsulating layer (bank) are formed of an application film using amaterial that has a backbone structure obtained by binding silicon (Si)to oxygen (O) and has one or more substituents selected from hydrogen,fluorine, an alkyl group, and aromatic hydrocarbon. A film after beingbaked corresponds to a silicon oxide film (SiOx) containing an alkylgroup. The silicon oxide film (SiOx) containing an alkyl group has ahigher light transmittance than acryl resin and can endure heattreatment at a temperature of 300° C. or more.

According to the invention, an interlayer insulating film and aninsulating layer (bank) are formed by an application method through thefollowing steps. First, in order to increase the wettability, thinnerpre-wet application is carried out after washing a substrate withpurified water, and a liquid material called a varnish in which a lowmolecular weight component (precursor) with binding of silicon (Si) tooxygen (O) is dissolved in a solvent is applied on the substrate by aspin coating method or the like. Then, the varnish as well as thesubstrate is heated to accelerate volatilization (evaporation) of thesolvent and crosslinking of the low molecular weight component, wherebya thin film can be obtained. Subsequently, an application film in aperipheral edge portion of the substrate is removed. In the case of aninsulating layer (bank) being formed, the film may be patterned toobtain a desired shape. The film thickness is controlled by the spinrotation rate, the rotation time, the concentration and the viscosity ofthe varnish.

The use of the same material for an interlayer insulating film and aninsulating layer (bank) will result in the reduction of themanufacturing cost. Further, since devices such as the one for coatingand for etching can be used in common, cost reduction can also beachieved.

In general, ITO (Indium Tin Oxide) is employed for a first electrode(anode or cathode) of an EL element that includes a light emitting layercontaining an organic compound. However, ITO has a high refractive indexof approximately 2. Thus, according to the invention, the firstelectrode is formed of indium tin oxide containing silicon oxide(hereinafter referred to as ITSO). Unlike ITO, ITSO is not crystallizedeven when baked and remains in the amorphous state. Accordingly, theplanarity of ITSO is superior to that of ITO, and the first electrodeusing ITSO is not short-circuited to the second electrode easily evenwhen a layer containing an organic compound is thin, thus, ITSO issuitable for an electrode of a display element. In addition, whensilicon oxide with a refractive index of approximately 1.46 is added,the refractive index of ITSO used as the first electrode can be changed.

Furthermore, a display device that includes ITSO for an electrode anduses for an interlayer insulating film a heat resistant planarized filmobtained by an application method generates less heat, leading toimproved reliability of the display device.

According to the display device of the invention, light from a lightemitting layer is emitted outside of a substrate through stacked layersformed of a material with high light transmittance, whereby increasedemission efficiency can be achieved.

According to the invention, a heat resistant planarized film, a firstelectrode, and an insulating layer (bank) are doped with at least oneelement selected from the elements belonging to Group 13 or Group 15 inthe periodic table, which are impurities of one conductivity type. Thedoping may be carried out by an ion doping method, a plasma dopingmethod, or an ion implantation method. As the elements belonging toGroup 13 or Group 15 in the periodic table, B, Al, Ga, In, Tl, P, As,Sb, and Bi can be employed, and typically phosphorous (P) and boron (B)are employed. At least one element selected from the elements belongingto Group 13 or Group 15 in the periodic table, which are relativelylarge in atomic diameter, is doped in order to generate distortions andmodify or densify the surface (including side walls), thereby preventingmoisture and oxygen from entering. In addition, the baking effect of thedoping itself allows moisture to be released during the treatment. Whenthe first electrode is also doped with at least one element selectedfrom the elements belonging to Group 13 or Group 15 in the periodictable, physical properties such as resistance can be controlled.

The dosage of at least one element selected from the elements belongingto Group 13 or Group 15 in the periodic table, which is included in thedoped region (densified area), may be substantially equal in the heatresistant planarized film, the first electrode and the insulating layer(bank). Specifically, the concentration is preferably in the range of1×10¹⁸ to 5×10²¹/cm³, and more preferably in the range of 2×10¹⁹ to2×10²¹/cm³. It is to be noted that when a side surface of the insulatinglayer and a side surface of the planarized film are inclined to have atapered shape, at least one element (ion species) selected from theelements belonging to Group 13 or Group 15 in the periodic table can beaccelerated in an electric field to affect the side surfaces, leading tomodification thereof. A taper angle at this time is preferably in therange between 30 and 75°.

According to the invention, in the case of, after forming a contacthole, an element with a conductivity being doped to the periphery of thecontact hole, it is possible not only to densify the periphery of thecontact hole but also to add the element with a conductivity to asemiconductor layer under the contact hole. Therefore, a high densityimpurity region can be formed in the semiconductor layer in aself-aligned manner.

At least one element selected from the elements belonging to Group 13 orGroup 15 in the periodic table may be doped to each of the heatresistant planarized film, the first electrode, and the insulating layer(bank), or may be doped to one or two of them. Alternatively, it may bedoped to the whole surface of them, or may be selectively doped to forma doped region partially. That is, only a side surface of the heatresistant planarized film may be doped with an element and covered witha sealing member, or a contact hole may be partially doped with anelement. Needless to say, an element may be doped to the whole surfaceto make a high density region.

According to the invention, a substance containing an organic materialcan be used for a heat resistant planarized film and an insulating layer(bank). When such a substance being doped with at least one elementselected from the elements belonging to Group 13 or Group 15 in theperiodic table, the light transmittance thereof is lowered and thesubstance is colored. The reflectivity thereof remains low. In the caseof the heat resistant planarized film being doped with at least oneelement selected from the elements belonging to Group 13 or Group 15 inthe periodic table, the transmittance and reflectivity thereof arelowered due to the doping and the heat resistant planarized film iscolored. In a top emission display device, the colored film can be usedas a light shielding film that provides the effect of protecting TFTcharacteristics and the like. Even in a dual emission or a bottomemission display device, when a passivation film is formed on a heatresistant planarized film, the passivation film is not colored by atleast one element selected from the elements belonging to Group 13 orGroup 15 in the periodic table, therefore, only a part that exposes theheat resistant planarized film in a contact hole, is colored anddensified. Accordingly, even in a dual emission or a bottom emissiondisplay device, light can be transmitted and extracted sufficiently. Thedensified area of a contact hole can prevent moisture from entering. Asa result, contamination such as moisture can be prevented from enteringthrough the contact hole, and thus the effect of preventing degradationof a display element is further enhanced.

Furthermore, when doping at least one element selected from the elementsbelonging to Group 13 or Group 15 in the periodic table, the lighttransmittance of an insulating layer (bank) is lowered and theinsulating layer is colored in black. Accordingly, the lighttransmittance of the insulating layer (bank) can be controlled so thatit is colored in black and used as a black matrix of a display device.According to the invention, an insulating layer (bank) can function as adensified barrier against contamination as well as a black matrix withlow light transmittance, low reflectivity, and improved opticalproperties. As a result, it is possible to provide an inexpensivedisplay device with improved yield and reliability.

According to one mode of the invention, a display device comprises adisplay area that includes a first electrode, an insulating layercovering an edge of the first electrode, a layer containing an organiccompound formed on the first electrode, and a second electrode. Thefirst electrode and the insulating layer are doped with an impurityelement of one conductivity type.

According to one mode of the invention, a display device comprises adisplay area that includes a first electrode, a thin film transistorconnected to the first electrode with a planarized film interposedtherebetween, an insulating layer covering an edge of the firstelectrode, a layer containing an organic compound formed on the firstelectrode, and a second electrode. The first electrode, the insulatinglayer, and a side surface of the planarized film are doped with animpurity element of one conductivity.

According to one mode of the invention, a display device comprises adisplay area that includes a first electrode, a thin film transistorconnected to the first electrode with a planarized film interposedtherebetween, an insulating layer covering an edge of the firstelectrode, a layer containing an organic compound formed on the firstelectrode, and a second electrode. Either a source electrode or a drainelectrode of the thin film transistor is connected to a semiconductorlayer through an opening portion of the planarized film. The firstelectrode, the insulating layer, and a side surface and the openingportion of the planarized film are doped with an impurity element of oneconductivity type.

In the aforementioned structures, the heat resistant planarized film andthe insulating layer (bank) may be formed of the same material, and maybe formed of a silicon oxide (SiOx) film containing an alkyl group. Theuse of the same material results in lowered manufacturing costs.Further, in the aforementioned structures, the first electrode may beformed of indium tin oxide containing silicon oxide (SiOx).

In the aforementioned structures, the semiconductor layer connected tothe source electrode and the drain electrode may be a high densityimpurity region that is formed when, after forming the opening portion(contact hole), the heat resistant planarized film is doped with atleast one element selected from the elements belonging to Group 13 orGroup 15 in the periodic table.

In the aforementioned structures, the insulating layer (bank) that isdoped with at least one element selected from the elements belonging toGroup 13 or Group 15 in the periodic table is colored, and may be usedas a black matrix (light shielding film).

In each of the aforementioned structures, the display element emitslight of red, green, blue, or white color.

According to one mode of the invention, a manufacturing method of adisplay device comprises the steps of: forming on a substrate having aninsulating surface a thin film transistor that includes a semiconductorlayer having a source region, a drain region, and a channel formingregion interposed therebetween, a gate insulating film, and a gateelectrode; forming a planarized film on an irregular surface due to theform of the thin film transistor; forming a source electrode and a drainelectrode that are connected to the source region and the drain regionrespectively; forming a first electrode connected to the drainelectrode; forming an insulating layer covering an edge of the firstelectrode; doping an impurity element of one conductivity to the firstelectrode and the insulating layer; forming a layer containing anorganic compound on the first electrode; and forming a second electrodeon the layer containing an organic compound.

According to one mode of the invention, a manufacturing method of adisplay device comprises the steps of: forming on a first substratehaving an insulating surface a thin film transistor that includes asemiconductor layer having a source region, a drain region, and achannel forming region interposed therebetween, a gate insulating film,and a gate electrode; forming a planarized film on an irregular surfacedue to the form of the thin film transistor; removing the planarizedfilm selectively to form a planarized film having a tapered shape at aperipheral edge portion of the first substrate; forming a sourceelectrode and a drain electrode that are connected to the source regionand the drain region respectively; forming a first electrode connectedto the drain electrode; forming an insulating layer covering an edge ofthe first electrode; doping an impurity element of one conductivity tothe first electrode, the insulating layer, and at least an edge of theplanarized film; forming a layer containing an organic compound on thefirst electrode; forming a second electrode on the layer containing anorganic compound; and attaching a second substrate to the firstsubstrate with a sealing member surrounding an outer edge of theplanarized film.

According to one mode of the invention, a manufacturing method of adisplay device comprises the steps of: forming on a first substratehaving an insulating surface a thin film transistor that includes asemiconductor layer having a source region, a drain region, and achannel forming region interposed therebetween, a gate insulating film,and a gate electrode; forming a planarized film on an irregular surfacedue to the form of the thin film transistor; removing the planarizedfilm selectively to form an opening portion extending to the sourceregion or the drain region and to form a planarized film having atapered shape at a peripheral edge portion of the first substrate;doping an impurity element of one conductivity to the opening portionand the edge of the planarized film, the source region and the drainregion; forming a high density impurity region in the source region andthe drain region; forming a source electrode and a drain electrode thatare connected to the source region and the drain region respectively;forming a first electrode connected to the drain electrode; forming aninsulating layer covering an edge of the first electrode; doping animpurity element of one conductivity to the first electrode and theinsulating layer; forming a layer containing an organic compound on thefirst electrode; forming a second electrode on the layer containing anorganic compound; and attaching a second substrate to the firstsubstrate with a sealing member surrounding an outer edge of theplanarized film.

In the aforementioned structures, at least one element selected from theelements belonging to Group 13 or Group 15 in the periodic table isdoped to the planarized film, the first electrode, and the insulatinglayer (bank) so that the dosage of the at least one element may be equalin the planarized film, the first electrode, and the insulating layer(bank) that are doped with the at least one element. More specifically,at least one element selected from the elements belonging to Group 13 orGroup 15 in the periodic table is doped to the planarized film, thefirst electrode, and the insulating layer (bank) so that theconcentration of the at least one element may be in the range of 1×10¹⁸to 5×10²¹/cm³, and more preferably in the range of 2×10¹⁹ to 2×10²¹/cm³.The doping may be carried out at an energy of 1 to 150 kV, and morepreferably at an energy of 50 to 80 kV, and at a dosage of 1×10¹⁴/cm² ormore, and more preferably at a dosage of 1×10¹⁵ to 1×10¹⁶/cm². It is tobe noted that when a side surface of the insulating layer and a sidesurface of the planarized film are inclined to have a tapered shape, atleast one element (ion species) selected from the elements belonging toGroup 13 or Group 15 in the periodic table can be accelerated in anelectric field to affect the side surfaces, leading to modificationthereof. A taper angle at this time is preferably in the range between30 and 75°.

As the elements belonging to Group 13 or Group 15 in the periodic table,B, Al, Ga, In, Tl, P, As, Sb, and Bi can be employed, and typically,phosphorous (P) and boron (B) are employed. At least one elementselected from the elements belonging to Group 13 or Group 15 in theperiodic table, which are relatively large in atomic diameter, is dopedin order to generate distortions, modify or densify the surface(including side walls), and thereby preventing moisture and oxygen fromentering. When the first electrode is also doped with at least oneelement selected from the elements belonging to Group 13 or Group 15 inthe periodic table, physical properties such as resistance can becontrolled.

In the aforementioned structures, the planarized film or the insulatinglayer (bank) is a silicon oxide (SiOx) film containing an alkyl group,which is formed by an application method. Further, in each of theaforementioned structures, an anode is formed by a sputtering methodusing indium tin oxide containing silicon oxide (SiOx) as a target.

In each of the aforementioned structures, the light emitting displaydevice can be applied to both an active matrix type and a passive matrixtype.

A light emitting element (EL element) as a display element comprises ananode, a cathode, and a layer containing an organic compound in whichluminescence can be obtained when an electric field is applied (electroluminescence). The luminescence in an organic compound includesluminescence that is generated when an is excited singlet state returnsto a ground state (fluorescence) and luminescence that is generated whenan excited triplet state returns to a ground state (phosphorescence). Alight emitting display device according to the invention can be appliedto both types of the luminescence.

A light emitting element (EL element) including an EL layer has astructure in which the EL layer is sandwiched between a pair ofelectrodes. In general, the EL layer has a laminated structure andtypically, a hole transporting layer, a light emitting layer, and anelectron transporting layer are laminated in this order. This structureprovides significantly increased emission efficiency, and almost all thelight emitting devices being studied and developed now adopt thisstructure.

As another structure, a hole injection layer, a hole transporting layer,a light emitting layer, and an electron transporting layer may belaminated on an anode in this order, or a hole injection layer, a holetransporting layer, a light emitting layer, an electron transportinglayer, and an electron injection layer may be laminated on an anode inthis order. The light emitting layer may be doped with a fluorescentpigment or the like. All of these layers may be formed of a lowmolecular weight material or a high molecular weight material.Alternatively, a layer containing an inorganic material may be employed.It is to be noted that in this specification, all the layers disposedbetween an electrode functioning as a cathode and an electrodefunctioning as an anode are collectively called an EL layer. Therefore,the EL layer includes all of the aforementioned hole injection layer,hole transporting layer, light emitting layer, electron transportinglayer, and electron injection layer.

In the light emitting device according to the invention, a drivingmethod of dual emission display is not exclusively limited. For example,a dot-sequential driving method, a line-sequential driving method, aframe-sequential driving method and the like may be employed. Typically,the line-sequential driving method is used, and a time gray scaledriving method and an area gray scale driving method may be adoptedappropriately. In addition, an image signal inputted to a source line ofthe light emitting display device may be either an analog signal or adigital signal, and a driver circuit and the like may be designedappropriately in accordance with the image signal.

In a light emitting display device using a digital video signal, a videosignal inputted to a pixel is driven by a constant voltage (CV) or aconstant current (CC). When a video signal is driven by a constantvoltage (CV), a voltage applied to a light emitting element is constant(CVCV) or a current supplied to a light emitting element is constant(CVCC). When a video signal is driven by a constant current (CC), avoltage applied to a light emitting element is constant (CCCV) or acurrent supplied to a light emitting element is constant (CCCC).

In this specification, light extraction efficiency means the rate oflight emission from the surface of a transparent substrate to theatmosphere relative to light emission of an element.

The invention can be applied to any type of TFT. For example, a top gateTFT, a bottom gate (inverted staggered) TFT, or a forward staggered TFTcan be adopted.

As an active layer of a TFT, an amorphous semiconductor film, asemiconductor film including a crystalline structure, a compoundsemiconductor film including an amorphous structure, and the like can beemployed appropriately. Further, as an active layer of a TFT, asemi-amorphous semiconductor film (also called a microcrystallinesemiconductor film) that is a semiconductor having an intermediatestructure between amorphous and crystalline (including singlecrystalline and polycrystalline) structures. This semiconductor has athird state that is stable in free energy and a crystalline regionhaving a short range order and a lattice distortion. At least a part ofthe semi-amorphous semiconductor film has crystal grains of 0.5 to 20 nmand Raman spectrum is shifted to the lower frequency band than 520 cm⁻¹.The semi-amorphous semiconductor has an x-ray diffraction pattern withpeaks at (111) and (220) that are considered to be due to Si crystallattice. Further, the semi-amorphous semiconductor film is mixed with atleast 1 atom % of hydrogen or halogen as the neutralizing agent fordangling bond. The semi-amorphous semiconductor can be obtained by glowdischarge decomposition of silicon gas (plasma CVD). As a silicon gas,SiH₄ can be used as well as Si₂H₆, SiH₂Cl₂, SiHCl₃, SiCl₄, SiF₄ or thelike. The silicon gas may be diluted by one or more noble gas elementsselected from H₂, H₂ and He, Ar, Kr, and Ne. In that case, the silicongas is diluted at a dilution rate of 2 to 1000, at a pressure of about0.1 to 133 Pa, a power supply frequency of 1 to 120 MHz, and morepreferably of 13 to 60 MHz. The substrate may be heated at a temperatureof 300° C. or less, and more preferably of 100 to 250° C. Among impurityelements added to the film, atmospheric elements such as oxygen,nitrogen and carbon desirably have a concentration of 1×10²⁰ cm⁻¹ orless. In particular, the concentration of oxygen is 5×10¹⁹ cm³ or less,and more preferably 1×10¹⁹ cm³ or less. The field effect mobility μ of aTFT using a semi-amorphous semiconductor film as an active layer is inthe range of 1 to 10 cm²/Vsec.

When an insulating layer used for a bank is doped with at least oneelement selected from the elements belonging to Group 13 or Group 15 inthe periodic table, a surface and a side surface of the insulating layerare modified and densified, and thereby moisture entering externally andmoisture included in the insulating layer are released so as not toadversely affect an EL layer. Accordingly, various defects such as adark spot and a shrink can be prevented, leading to improved reliabilityof a display device.

When doping at least one element selected from the elements belonging toGroup 13 or Group 15 in the periodic table, the resistivity of a firstelectrode can be controlled. Therefore, electrical properties of theelectrode can be controlled so that the emission efficiency, theluminance and the like of a display device may be increased.

At the same time, when an insulating layer covering an edge of the firstelectrode is doped with at least one element selected from the elementsbelonging to Group 13 or Group 15 in the periodic table, the lighttransmittance of the insulating layer can be lowered so as to be used asa light shielding film (black matrix). As a result, the number ofmanufacturing steps is reduced, leading to lower cost and improved yieldof the display device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1D are diagrams showing a configuration of the invention.

FIGS. 2A and 2B are diagrams showing a configuration of the invention.

FIGS. 3A to 3D are diagrams showing a configuration of the invention.

FIGS. 4A and 4B are diagrams showing a configuration of the invention.

FIG. 5 is a diagram showing a configuration of the invention.

FIGS. 6A to 6D are diagrams showing a configuration of the invention.

FIG. 7 is a diagram showing a configuration of the invention.

FIG. 8 is a diagram showing a configuration of the invention.

FIGS. 9A to 9D are diagrams showing a configuration of the invention.

FIGS. 10A and 10B are diagrams showing a configuration of the invention.

FIGS. 11A to 11D are diagrams showing a configuration of the invention.

FIGS. 12A and 12B are diagrams showing a configuration of the invention.

FIG. 13 is a cross sectional view of a display device of the invention.

FIG. 14 is a cross sectional view of a display device of the invention.

FIG. 15 is a cross sectional view of a display device of the invention.

FIG. 16 is a cross sectional view of a display device of the invention.

FIG. 17 is a cross sectional view of a display device of the invention.

FIG. 18 is a cross sectional view of a display device of the invention.

FIG. 19 is a cross sectional view of a display device of the invention.

FIG. 20 is a top plan view of a display device of the invention.

FIGS. 21A to 21E are views showing display devices of the invention.

FIG. 22 is a view showing a display device of the invention.

FIG. 23 is a graph showing reflectivity.

FIG. 24 is a graph showing electrical properties.

FIG. 25 is a cross sectional view of a display device of the invention.

FIG. 26 is a cross sectional view of a display device of the invention.

FIG. 27 is a graph showing results of TDS measurement.

FIG. 28 is a graph showing results of SIMS measurement.

FIGS. 29A and 29B are top plan views of a display device of theinvention.

FIG. 30 is a graph showing transmittance.

DETAILED DESCRIPTION OF THE INVENTION Embodiment Mode 1

An embodiment mode of the invention is described hereinafter.

A base film 101 is formed on a substrate 100 having an insulatingsurface. As the base film 101, a silicon oxynitride film 101 b with athickness of 10 to 200 nm (preferably 50 to 100 nm) is formed by plasmaCVD and a silicon oxynitride film 101 a with a thickness of 50 to 200 nm(preferably 100 to 150 nm) is formed thereon. It is possible to use asthe substrate 100 a glass substrate, a quartz substrate, a siliconsubstrate, a metal substrate or a stainless substrate each of which hasa surface covered with an insulating film. Alternatively, a plasticsubstrate having a heat resistance at a treatment temperature of thisembodiment mode may be employed as well as a flexible substrate. Thebase film may have a two-layer structure, or may be formed of a singleor two or more base (insulating) films.

Then, a semiconductor film is formed on the base film 101. Thesemiconductor film may be formed by a known method (sputtering, LPCVD,plasma CVD or the like) so as to have a thickness of 25 to 200 nm(preferably 30 to 150 nm). A material of the semiconductor film is notexclusively limited, though it is preferably formed of silicon, an alloyof silicon and germanium (SiGe), and the like.

For the semiconductor film, an amorphous semiconductor (typified byamorphous silicon hydride), or a crystalline semiconductor (typified bypolysilicon) is employed. Polysilicon includes a so-called hightemperature polysilicon that mainly uses polycrystalline silicon formedat a process temperature of 800° C. or more, a so-called low temperaturepolysilicon that mainly uses polycrystalline formed at a processtemperature of 600° C. or less, a crystalline silicon that iscrystallized by doping an element for promoting crystallization thereto,and the like.

As the semiconductor film, a semi-amorphous semiconductor or asemiconductor having a crystalline phase in a part of a semiconductorfilm may be used as well. The semi-amorphous semiconductor is asemiconductor having an intermediate structure between amorphous andcrystalline (including single crystalline and polycrystalline)structures. This semiconductor has a third state that is stable in freeenergy, and it is a kind of a crystalline semiconductor that has a shortrange order and a lattice distortion. The semi-amorphous semiconductortypically includes silicon as a main component, and Raman spectrum isshifted to the lower frequency band than 520 cm⁻¹ due to the latticedistortion. Further, the semiconductor is mixed with at least 1 atom %of hydrogen or halogen as the neutralizing agent for dangling bond. Sucha semiconductor is called herein a semi-amorphous semiconductor (SAS).The SAS is also called a microcrystalline semiconductor (typicallymicrocrystalline silicon).

The SAS can be obtained by glow discharge decomposition of silicon gas.Typically, SiH₄ is used as a silicon gas, though Si₂H₆, SiH₂Cl₂, SiHCl₃,SiCl₄, SiF₄ or the like may be used as well. The formation of the SAScan be facilitated by using the silicon gas that is diluted by adding asingle or a plurality of noble gas elements selected from hydrogen,hydrogen and helium, argon, krypton, and neon. The silicon gas ispreferably diluted at a dilution rate of 5 to 1000. It is needless tosay that the formation of the SAS by glow discharge decomposition isdesirably performed under reduced pressure, but discharge underatmospheric pressure can also be utilized. Typically, the pressure maybe in the range of about 0.1 to 133 Pa. The power supply frequency forgenerating the glow discharge is in the range of 1 to 120 MHz, and morepreferably in the range of 13 to 60 MHz. An RF power may be setappropriately. The substrate is preferably heated at a temperature of300° C. or less, and more preferably 100 to 200° C. Among impurityelements that are mainly doped during deposition, atmospheric elementssuch as oxygen, nitrogen and carbon desirably have a concentration of1×10²⁰ cm⁻³ or less. In particular, the concentration of oxygen is5×10¹⁹ cm⁻³ or less, and more preferably 1×10¹⁹ cm⁻³ or less. When anoble gas element such as helium, argon, krypton, or neon is mixed intoan SAS, the lattice distortion is increased and the stability is thusenhanced, leading to a good SAS.

In the case of a crystalline semiconductor film being used as thesemiconductor film, it may be formed by a known method (lasercrystallization, thermal crystallization, or thermal crystallizationusing an element such as nickel for promoting crystallization, and thelike). Without introducing an element for promoting crystallization,hydrogen included in the amorphous silicon film may be released to lowerthe hydrogen concentration to 1×10²⁰ atoms/cm³ or less by heating in anitrogen atmosphere at a temperature of 500° C. for one hour, then laserlight is irradiated to the amorphous silicon film. This is performedbecause the amorphous silicon film is damaged by laser irradiation whenthe film contains much hydrogen.

A method for doping a metal element into the amorphous semiconductorfilm is not exclusively limited as long as the metal element can existon the surface of or inside the amorphous semiconductor film, and amethod such as sputtering, CVD, plasma treatment (including plasma CVD),adsorption, or a method for applying a metal salt solution can beemployed. Among them, a method using a solution is simple and easy, andis effective in adjusting the concentration of the metal element.Further, at this time, an oxide film is preferably formed by UV rayirradiation in an oxygen atmosphere, thermal oxidation, treatment withozone water or hydrogen peroxide including hydroxyl radical, or the likein order to improve wettability of the surface of the amorphoussemiconductor film and to spread water solution over an entire surfaceof the amorphous semiconductor film.

The amorphous semiconductor film may be crystallized by combining heattreatment and laser irradiation, and the heat treatment and the laserirradiation may be performed several times independently. In the case ofthe film being crystallized by heat treatment and laser irradiation,after doping the metal element, heat treatment is performed at atemperature of 500 to 550° C. for 4 to 20 hours to crystallize theamorphous semiconductor film (hereinafter referred to as a firstcrystalline semiconductor film).

Subsequently, a second crystalline semiconductor film is obtained byirradiating the first crystalline semiconductor film with laser light topromote crystallization. Laser crystallization is a method forirradiating the semiconductor film with laser light. As for the laser, asolid-state laser, a gas laser, or a metal laser of pulse oscillation orcontinuous wave oscillation is preferably used. The solid-state laserincludes a YAG laser, a YVO₄ laser, a YLF laser, a YAIO₃ laser, a glasslaser, a ruby laser, an alexandrite laser, a Ti:sapphire laser and thelike. The gas laser includes an excimer laser, an Ar laser, a Kr laser,a CO₂ laser and the like. The metal layer includes a helium cadmiumlaser, a copper vapor laser, and a gold vapor laser. The laser beam maybe converted to a harmonic by a non-linear optical element. A crystalused for the non-linear optical element such as LBO, BBO, KDP, KTP, KB5,or CLBO has the advantage of conversion efficiency. The conversionefficiency can be drastically increased by introducing these non-linearoptical elements into a laser resonator. A laser of the harmonic istypically doped with Nd, Yb, Cr or the like, which are excited tooscillate a laser. A kind of the dopant may be selected appropriately.

After forming the crystalline semiconductor film in such a manner, avery small amount of impurity element (boron or phosphorous) is doped tocontrol a threshold voltage of a TFT.

The semiconductor film is patterned by photolithography using a firstphotomask to obtain a semiconductor layer 102.

A gate insulating film 105 is formed so as to cover the semiconductorlayer 102. The gate insulating film 105 is formed of an insulating filmcontaining silicon by plasma CVD or sputtering so as to have a thicknessof 40 to 150 nm. It is needless to say that the gate insulating film isnot limited to a silicon oxynitride film, and it may be formed of asingle or a plurality of other insulating films.

Subsequently, a first conductive film with a thickness of 20 to 100 nmand a second conductive film with a thickness of 100 to 400 nm arelaminated in this order on the gate insulating film 105 to be used as agate electrode. The first conductive film and the second conductive filmmay be formed of an element selected from Ta, W, Ti, Mo, Al, and Cu, oran alloy or a compound mainly containing the element. Alternatively, thefirst conductive film and the second conductive film may be formed of anAgPdCu alloy as well as a semiconductor film typified by apolycrystalline silicon film doped with an impurity element such asphosphorous. The conductive film is not limited to a two-layerstructure, and may be a three-layer structure in which, for instance, atungsten film with a thickness of 50 nm, an alloy film of aluminum andsilicon (Al—Si) with a thickness of 500 nm, and a titanium nitride filmwith a thickness of 30 nm are laminated in this order. In the case ofthe three-layer structure being adopted, tungsten nitride may be usedinstead of tungsten as the first conductive film, an alloy film ofaluminum and titanium (Al—Ti) may be used instead of the alloy film ofaluminum and silicon (Al—Si) as the second conductive film, and atitanium film may be used instead of the titanium nitride film as thethird conductive film. Alternatively, the conductive layer may have asingle layer structure.

A second photomask using a resist is formed by photolithography toperform a first etching step for obtaining an electrode and a wiring.The first conductive film and the second conductive film can be etchedso as to be have a desired tapered shape by ICP (Inductively CoupledPlasma) etching when etching conditions (amount of power applied to acoiled electrode, amount of power applied to an electrode on thesubstrate side, temperature of the electrode on the substrate side, andthe like) are adjusted appropriately. As etching gas, chlorine gastypified by Cl₂, BCl₃, SiCl₄, CCl₄ or the like, or fluorinated gastypified by CF₄, SF₆, NF₃ or the like, can be employed appropriately aswell as O₂.

Obtained by the first etching step is a conductive layer having a firstshape, which includes a first conductive layer and a second conductivelayer.

Then, a second etching step is performed without removing the mask usinga resist. A W film is selectively etched herein. At this time, thesecond conductive layer is formed by the second etching step. On theother hand, the first conductive layer is hardly etched to form aconductive layer having a second shape. Accordingly, a conductive film106 and a conductive film 107 are obtained. Although the conductivelayers are formed by dry etching in this embodiment mode, they may beformed by wet etching.

After removing the resist mask, a resist mask as a third photomask isformed. Then, in order to form an N-channel TFT that is not shown in thedrawing, a first doping step is performed to dope an impurity elementthat imparts an N-type conductivity (typically, phosphorous (P) orarsenic (As)) to a semiconductor at a low density. The resist maskcovers an area to be used for a P-channel TFT and a periphery of theconductive layers. By the first doping step, through doping is performedthrough an insulating film to form a low density impurity region. Onelight emitting element is driven by a plurality of TFTs, however, in thecase of the light emitting element being driven by P-channel TFTs only,the aforementioned doping step can be omitted.

After removing the resist mask, a resist mask as a fourth photomask isformed. Then, a second doping step is performed in order to dope animpurity element that imparts a P-type conductivity (typically, boron(B)) to a semiconductor at a high density. By the second doping step,through doping is performed through the gate insulating film 105 to formhigh density impurity regions 103 and 104.

Subsequently, a resist mask as a fifth photomask is formed. Then, inorder to form an N-channel TFT that is not shown in the drawing, a thirddoping step is performed to dope an impurity element that imparts anN-type conductivity (typically, P or As) to a semiconductor at a highdensity. The conditions of the third doping step are such that thedosage is in the range of 1×10¹³ to 5×10¹⁵/cm² and the acceleratingvoltage is in the range of 60 to 100 keV. The resist mask covers an areato be used for a P-channel TFT and a periphery of the conductive layers.By the third doping step, through doping is performed through the gateinsulating film 105 to form an N-type high density impurity region.

In this manner, an impurity region is formed in each of thesemiconductor layers.

Then, the resist mask is removed and an insulating film 108 containinghydrogen is formed as a passivation film. The insulating film 108 isformed of an insulating film containing silicon by plasma CVD orsputtering so as to have a thickness of 100 to 200 nm. The insulatingfilm 108 is not limited to a silicon nitride film and may be formed of asilicon nitride oxide (SiNO) film by plasma CVD. Alternatively, theinsulating film 108 may be formed of a single or a plurality of otherinsulating films containing silicon.

Furthermore, heat treatment is carried out in a nitrogen atmosphere at atemperature of 300 to 550° C. (preferably 400 to 500° C.) for 1 to 12hours, and a hydrogenation step of the semiconductor layers isperformed. This step is carried out for terminating dangling bonds ofthe semiconductor layers by hydrogen contained in the insulating film108.

The insulating film 108 is formed of a material selected from siliconnitride, silicon oxide, silicon oxynitride (SiON), silicon nitride oxide(SiNO), aluminum nitride (AlN), aluminum oxynitride (AlON), aluminumnitride oxide (AlNO) that contains more nitrogen than oxygen, aluminumoxide, diamond like carbon (DLC), and a carbon film containing nitrogen(CN). It is also possible to use a material that has a backbonestructure obtained by binding silicon (Si) to oxygen (O) and has atleast a hydrogen substituent, or a material that has one or moresubstituents selected from fluorine, an alkyl group, and aromatichydrocarbon.

In order to activate the impurity element, heat treatment, intense lightirradiation, or laser irradiation may be carried out. In addition to theactivation, plasma damage to the gate insulating film can be recoveredas well as plasma damage to an interface between the gate insulatingfilm and the semiconductor layers.

Subsequently, a heat resistant planarized film 109 functioning as aninterlayer insulating film is formed. The heat resistant planarized film109 is formed by using an insulating film that has a backbone structureobtained by binding silicon (Si) to oxygen (O) and that is obtained byan application method.

Forming steps of the heat resistant planarized film 109 are hereinafterdescribed in detail.

First, purified water cleaning of a substrate to be processed isperformed. Megasonic cleaning may also be performed. After dehydrobakingbeing performed at a temperature of 140° C. for 110 seconds, atemperature of the substrate is regulated by cooling with a water-cooledplate for 120 seconds. Next, the substrate is transferred to be placedin a spin coating apparatus.

The spin coating apparatus comprises a nozzle and an application cup.The spin coating apparatus has a mechanism in which the solution of anapplied material is dropped on the substrate, the substrate is placedhorizontally in the application cup, and the entire application cuprotates. The spin coating apparatus also has a mechanism in which thepressure of atmosphere in the application cup can be controlled.

Subsequently, pre-wet application is carried out to improve wettabilitywith the use of an organic solvent such as thinner (a volatile mixturesolvent formed by mixing aromatic hydrocarbon (toluene or the like),alcohols, ester acetate and the like). The thinner is thoroughly spreadby centrifugal force by spinning the substrate (rotation rate of 100rpm) while dropping 70 ml of the thinner, then, the thinner is thrownoff by spinning the substrate at high speed (rotation rate of 450 rpm).

Then, the solution of the applied material prepared by dissolvingsiloxane based polymer in a solvent (propylene glycolmonomethyl ether)is thoroughly spread by centrifugal force while gradually spinning(rotation rate from 0 to 1000 rpm) the substrate and dropping thesolution of the applied material from the nozzle. Siloxane can beclassified into, for example, silica glass, alkylsiloxane polymer,alkylsilsesquioxane polymer, hydrogenated silsesquioxane polymer,hydrogenated alkylsilsesquioxane polymer and the like according to thestructure thereof. As examples of the siloxane based polymer, there arePSB-K1 or PSB-K31 as a material of an application insulating filmproduced by Toray, and ZRS-5PH as a material of an applicationinsulating film produced by Shokubai Kasei. After holding the substratefor approximately 30 seconds, the substrate is gradually spun (rotationrate from 0 to 1400 rpm) again to level a film formed by the applicationstep.

Inside of the application cup is exhausted to reduce the pressure, andthen reduced-pressure drying is performed for within one minute.

Edge removing treatment is performed then by an edge remover equipped inthe spin coating apparatus. The edge remover comprises a moving meansthat moves in parallel along the periphery of the substrate. The edgeremover also comprises a thinner spraying nozzle so as to sandwich oneside of the substrate, and the application film at the peripheral edgeportion of the substrate is dissolved by the thinner, thereby theapplication film at the peripheral edge portion of the substrate edge isremoved by evacuating liquid and gas.

Then, prebaking is carried out by performing baking at a temperature of110° C. for 170 seconds.

The substrate is transferred from the spin coating apparatus and cooled.Afterwards, baking is further carried out at a temperature of 270° C.for one hour. Thus, the heat resistant planarized film 109 with athickness of 0.8 μm is obtained. When the planarity of the obtained heatresistant planarized film 109 is observed by an AFM (Atomic ForceMicroscope) within an area of 10 μm×10 μm, the peak to valley (P-V)value (difference between the highest and the lowest values) isapproximately 5 nm and the surface roughness Ra is approximately 1.3 nm.

The transmittance of the heat resistant planarized film 109 can bechanged by varying baking temperature of the film. When thetransmittance and refractive index of the heat resistant planarized film109 (SiOx film containing an alkyl group) with a thickness of 0.8 μm ismeasured at baking temperatures of 270° C. and 410° C., thetransmittance is increased and the reflective index is lowered in thecase of 410° C. as compared with the case of 270° C.

In such a manner, the heat resistant planarized film 109 is obtained.

The heat resistant planarized film 109 may be formed by ink-jet. Amaterial solution can be saved by the use of ink-jet.

The heat resistant planarized film 109 may be formed of an insulatingfilm that has a backbone structure obtained by binding silicon (Si) tooxygen (O) as well as a film including a single or more kinds ofmaterials having high heat resistance and high planarization rate, suchas an inorganic material (silicon oxide, silicon nitride, siliconoxynitride, silicon nitride oxide and the like), a photosensitive ornon-photosensitive organic material (organic resin material) (polyimide,acryl, polyamide, polyimide amide, resist, benzocyclobutene and thelike), and a Low k material as a low dielectric constant material.Alternatively, films including these materials may be laminated to beused as the heat resistant planarized film 109.

Subsequently, an insulating film 111 is formed as a passivation film(see FIG. 1A). The insulating film 111 is formed of an insulating filmcontaining silicon by plasma CVD or sputtering so as to have a thicknessof 100 to 200 nm. When patterning a wiring 112 (used as a drainelectrode or a source electrode) in subsequent steps, the insulatingfilm 111 is used as an etching stopper film for protecting the heatresistant planarized film 109 that functions as an interlayer insulatingfilm.

Needless to say, the insulating film 111 is not limited to a siliconoxynitride film, and may be formed of a single or a plurality of layersof other insulating films containing silicon. Although a silicon nitridefilm formed by sputtering is used in this embodiment mode, a siliconnitride oxide (SiNO) film formed by plasma CVD may be employed as well.In this embodiment mode, Ar in the film has a concentration ofapproximately 5×10¹⁸ to 5×10²⁰ atoms/cm³.

The insulating film 111 is formed of a material selected from siliconnitride, silicon oxide, silicon oxynitride (SiON), silicon nitride oxide(SiNO), aluminum nitride (AlN), aluminum oxynitride (AlON), aluminumnitride oxide (AlNO) that contains more nitrogen than oxygen, aluminumoxide, diamond like carbon (DLC), and a carbon film containing nitrogen(CN). It is also possible to use, as in this embodiment mode, a materialthat has a backbone structure obtained by binding silicon (Si) to oxygen(O) and has at least a hydrogen substituent, or a material that has oneor more substituents selected from fluorine, an alkyl group, andaromatic hydrocarbon.

The heat resistant planarized film 109 at a peripheral edge portion ofthe substrate is removed simultaneously with the formation of a contacthole 130 in the heat resistant planarized film 109 with the use of aresist mask. Etching (wet etching or dry etching) is performed hereinunder the conditions that high etch selectivity is secured relative tothe insulating film. Etching gas to be used may be added with inert gas.As the inert gas, a single or more kinds of gas selected from He, Ne,Ar, Kr, and Xe can be used. Among them, argon that is inexpensive andrelatively large in atomic diameter is preferably employed. In thisembodiment mode, CF₄, O₂, He, and Ar are used. Dry etching is performedby setting the flow of CF₄ at 380 sccm; O₂, 290 sccm; He, 500 sccm; Ar,500 sccm; RF power, 3000 W; and pressure, 25 Pa. According to suchconditions, etching residue can be reduced.

Note that, the etching time may be increased at the rate ofapproximately 10 to 20% for etching the gate insulating film 105 withoutleaving a residue on its surface. One time of etching or plural times ofetching may be conducted to obtain a tapered shape. In addition, thetapered shape may be obtained by performing the second dry etching withthe use of CF₄, O₂, and He by setting the flow of CF₄ at 550 sccm; O₂,450 sccm; He, 350 sccm; RF power, 3000 W; and pressure, 25 Pa. A taperangle at the edge of the heat resistant planarized film 109 is desirablyin the range between 30 to 75°.

The heat resistant planarized film 109 at a peripheral portion of thesubstrate may be doped with at least one element selected from theelements belonging to Group 13 or Group 15 in the periodic table to forma densified area in the tapered portion of the heat resistant planarizedfilm 109. The doping may be carried out by an ion doping method, aplasma doping method, or an ion implantation method. As the elementsbelonging to Group 13 or Group 15 in the periodic table, B, Al, Ga, In,Ti, P, As, Sb, and Bi can be employed, and typically phosphorous (P) andboron (B) are employed. At least one element selected from the elementsbelonging to Group 13 or Group 15 in the periodic table, which arerelatively large in atomic diameter, is doped in order to generatedistortions and modify or densify the surface (including side walls),thereby preventing moisture and oxygen from entering. In addition, thebaking effect of the doping itself allows moisture to be released duringthe treatment. At least one element selected from the elements belongingto Group 13 or Group 15 in the periodic table, which is included in thedensified area, has a concentration of 1×10¹⁸ to 5×10²¹/cm³, andtypically 2×10¹⁹ to 2×10²¹/cm³. It is to be noted that the tapered shapeof the heat resistant planarized film at the peripheral edge portion ofthe substrate allows the side surface of the heat resistant planarizedfilm 109 to be doped easily.

In the case of the heat resistant planarized film 109 being doped withat least one element selected from the elements belonging to Group 13 orGroup 15 in the periodic table, the transmittance and reflectivity arelowered due to the doping and the heat resistant planarized film 109 iscolored. In a top emission display device, the colored film can be usedas a light shielding film that provides the effect of protecting TFTcharacteristics and the like. Even in a dual emission or a bottomemission display device, when the insulating film 111 as a passivationfilm is formed on the heat resistant planarized film 109 as in thisembodiment mode, the passivation film is not colored by at least oneelement selected from the elements belonging to Group 13 or Group 15 inthe periodic table. Therefore, only a part that exposes the heatresistant planarized film 109 in the contact hole is colored anddensified. Accordingly, even in a dual emission or a bottom emissiondisplay device, light can be transmitted and extracted sufficiently. Thedensified area of the contact hole can prevent moisture from entering.As a result, contamination such as moisture can be prevented fromentering through the contact hole, and thus the effect of preventingdegradation of a display element is further enhanced.

The gate insulating film 105 is etched to form an opening portion thatextends to a source region or a drain region. In order to form theopening portion, the insulating film 108 and the gate insulating film105 may be etched with a mask that is formed after etching the heatresistant planarized film 109 or with the etched heat resistantplanarized film 109 used as a mask. The gate insulating film 105 isetched by using CHF₄ and Ar as etching gas. By the etching step undersuch conditions, the contact hole that has a surface with fewirregularities and has a high planarization rate can be obtained whilereducing etching residue. It is to be noted that the etching time may beincreased at the rate of approximately 10 to 20% to perform the etchingwhile further reducing residues on the semiconductor layer. Through theaforementioned steps, a contact hole 130 is formed (see FIG. 1B).

A metal film is formed and etched to form a wiring 112 that iselectrically connected to each impurity region. The wiring 112 functionsalso as a source electrode or a drain electrode. For the metal film,elements such as aluminum (Al), titanium (Ti), molybdenum (Mo), tungsten(W), and silicon (Si) may be used as well as an alloy film using theseelements. In this embodiment mode, TiN, Al, and TiN are laminated so asto have a thickness of 100 nm, 350 nm, and 100 nm respectively, and thenpatterned to make a desired shape, thereby forming the wiring 112 (seeFIG. 1C). Note that TiN is one of the materials having excellentadhesiveness with the heat resistant planarized film. When silicon oxide(SiOx) containing an alkyl group is used for the heat resistantplanarized film and Ti is laminated as the wiring, a Si—O—Ti bindingoccurs at the interface, which produces an O—Ti binding a. On the otherhand, when TiN is laminated as the wiring, a Si—N—Ti binding occurs atthe interface, which produces a Si—N binding b and an N—Ti binding c.Since the O—Ti binding has a weak binging strength, it does not exhibitexcellent adhesiveness. However, the Si—N binding b and the N—Ti bindingc have a strong binding strength, therefore, they exhibit excellentadhesiveness and the film is not easily peeled off. In addition, TiNpreferably contains N with a concentration of less than 44 atomic % inorder to form a contact with the source region or the drain region ofthe TFT. More preferably, the concentration of N is contained in TiN isin the range between 7 and 44 atomic %. The conductive film may have atwo-layer structure of TiN/Al, leading to simplification of themanufacturing steps.

Etching is carried out by ICP (Inductively Coupled Plasma) using BCl₃and Cl₂. Etching conditions are such that the amount of power applied toa coiled electrode is 450 W; the amount of power applied to an electrodeon the substrate side is 100 W; and pressure is 1.9 Pa. At this time,the insulating film 111 that has been formed previously functions as anetching stopper. When the wiring 112 and the insulating film 111 havehigh etch selectivity, the insulating film 111 can be planarized withoutleaving a residue on the surface thereof. The insulating film 111 havinghigh planarization rate prevents a first electrode formed on theinsulating film 111 as a pixel electrode from being broken orshort-circuited, leading to improved reliability of a display device.

Through the aforementioned steps, an active matrix substrate having aTFT is completed. Although only a P-channel TFT is formed in a pixelregion in this embodiment mode, an N-channel TFT may also be formed andthe N-channel TFT may have a single gate structure including one channelforming region, a double gate structure including two channel formingregions, or a triple gate structure including three channel formingregions. Furthermore, a TFT in a driver circuit may also have a singlegate structure, a double gate structure, or a triple gate structure.

The manufacturing method of a TFT is not limited to the one shown inthis embodiment mode. The invention can be applied to a top gate(planer) TFT, a bottom gate (inverted staggered) TFT, a dual gate TFTthat has two gate electrodes above and below a channel region with gateinsulating films interposed therebetween, or other types of TFTs.

Subsequently, a first electrode (referred to as a pixel electrode) 113is formed so as to be connected to the wiring 112. The first electrode113 functions as an anode or a cathode. The first electrode 113 may beformed of a film or a laminated film that mainly includes an elementselected from Ti, TiN, TiSi_(X)N_(Y), Ni, W, WSi_(X), WN_(X),WSi_(X)N_(Y), NbN, Cr, Pt, Zn, Sn, In, and Mo, or an alloy or a compoundbased on the element, which has a total thickness of 100 to 800 nm.

This embodiment mode adopts a structure in which a light emittingelement is used as a display element and light from the light emittingelement is extracted from the first electrode side, therefore, the firstelectrode transmits light. A transparent conductive film is formed andetched to be a desired shape to form the first electrode 113. As thefirst electrode 113, a transparent conductive film such as ITO, IZO,ITSO, and indium oxide mixed with zinc oxide (ZnO) of 2 to 20% may beemployed. Alternatively, a titanium nitride film or a titanium film mayalso be used as the first electrode 113. In that case, after forming thetransparent conductive film, a titanium nitride film or a titanium filmis formed to be thin enough to transmit light (preferably about 5 to 30nm). In this embodiment mode, ITSO is used as the first electrode 113.Unlike ITO, ITSO is not crystallized even when baked and remains in theamorphous state. Accordingly, the planarity of ITSO is superior to thatof ITO, and the first electrode using ITSO is not short-circuited to thecathode easily even when a layer containing an organic compound is thin.The first electrode 113 may be swabbed by a polyvinyl alcohol basedporous body and polished by CMP so that the surface thereof may beplanarized. In addition, after being polished by CMP, the surface of thefirst electrode 113 may be irradiated with UV rays or treated withoxygen plasma and the like.

Then, an insulator (insulating layer) 114 (referred to as a bank, abarrier or the like) is formed so as to cover the edge of the firstelectrode 113 and the wiring 112. As the insulator 114, an SOG film (forexample, a SiO_(X) film containing an alkyl group) is formed by anapplication method so as to have a thickness of 0.8 to 1 μm. Etching maybe either dry etching or wet etching. Here, the insulator 114 is formedby dry etching using a mixed gas of CF₄, O₂ and He (see FIG. 1D). Thedry etching is performed under such conditions as 5 Pa of pressure, 1500W, 25 sccm of CF₄, 25 sccm of O₂, and 50 sccm of He. In this dry etchingstep, the etching rate of the SiOx film containing an alkyl group is inthe range of 500 to 600 nm/min whereas the etching rate of the ITSO filmis 10 nm/min or less, thus, they can have sufficiently high etchselectivity. Further, since the wiring 112 is covered with the insulator114 formed of the SiOx film containing an alkyl group, a TiN film havingexcellent adhesiveness is the outer surface. The insulator 114 may beformed of an insulating film that has a backbone structure obtained bybinding silicon (Si) to oxygen (O) as well as a film including a singleor more kinds of materials having high heat resistance and highplanarization rate, such as an inorganic material (silicon oxide,silicon nitride, silicon oxynitride, silicon nitride oxide and thelike), a photosensitive or non-photosensitive organic material (organicresin material) (polyimide, acryl, polyamide, polyimide amide, resist,benzocyclobutene and the like), and a Low k material as a low dielectricconstant material. Alternatively, films including these materials may belaminated to be used as the insulator 114.

According to the invention, the edge of the heat resistant planarizedfilm 109, the first electrode 113, and the insulator 114 are doped withat least one element selected from the elements belonging to Group 13 orGroup 15 in the periodic table. As the elements belonging to Group 13 orGroup 15 in the periodic table, B, Al, Ga, In, Tl, P, As, Sb, and Bi canbe employed, and typically phosphorous (P) and boron (B) are employed.The doping may be carried out by an ion doping method, a plasma dopingmethod, or an ion implantation method. In this embodiment mode, a gas125 containing B as at least one element selected from the elementsbelonging to Group 13 or Group 15 in the periodic table is doped to formdoped regions 116, 117 and 118 (see FIG. 2A). According to theinvention, the doped regions 116, 117 and 118 in the heat resistantplanarized film 109 and the insulator 114 are densified. Further, in thedoped region 117 in the first electrode 113, physical properties such asresistance can be controlled. At least one element selected from theelements belonging to Group 13 or Group 15 in the periodic table, whichare relatively large in atomic diameter, is added in order to generatedistortions, modify or densify the surface (including side walls), andthereby preventing moisture and oxygen from entering. In addition, thebaking effect of the doping itself allows moisture to be released duringthe treatment. At least one element selected from the elements belongingto Group 13 or Group 15 in the periodic table, which is included in thedoped regions, has a concentration of 1×10¹⁸ to 5×10²¹/cm³, andtypically 2×10¹⁹ to 2×10²¹/cm³. It is to be noted that the tapered shapeof the edge of the heat resistant planarized film allows the sidesurface of the heat resistant planarized film 109 to be doped easily.The doping may be carried out at an energy of 1 to 150 kV, and morepreferably at an energy of 50 to 80 kV, and at a dosage of 1×10¹⁴/cm² ormore, and more preferably at a dosage of 1×10¹⁵ to 1×10¹⁶/cm². In a casethat phosphorous (P) is doped to the surface of the heat resistantplanarized film or insulating layer, phosphorous exists up to about 5000Å in the depth direction from the surface to which phosphorous is added.In a case that boron (B) is doped, boron exists up to about 8000 Å inthe depth direction from the surface to which boron is added.

When doping at least one element selected from the elements belonging toGroup 13 or Group 15 in the periodic table, the doped region 118 in theinsulator (insulating layer) 114 functioning as a bank is colored inblack. Accordingly, the insulating layer (bank) can be used as a blackmatrix. Thus, according to the invention, the insulating layer (bank)can function as a densified barrier against contamination as well as ablack matrix with low light transmittance, low reflectivity, andimproved optical properties. As a result, it is possible to provide aninexpensive display device with improved yield and reliability.

In order to improve reliability, it is preferable to perform vacuumheating before forming a light emitting layer 119 containing an organiccompound, thereby performing degasification. For example, it ispreferable to perform heat treatment at a temperature of 200 to 300° C.under a reduced pressure atmosphere or an inert atmosphere in order toremove gas contained in the substrate, before evaporating an organiccompound material. Since the interlayer insulating film and theinsulating layer (bank) are herein formed of a SiOx film having highheat resistance, heat treatment at a high temperature can be carried outwithout any problem. Accordingly, heat treatment steps for improvingreliability can be performed sufficiently.

The light emitting layer 119 is formed on the first electrode 113 (dopedregion 117). Although FIGS. 2E and 2F show one pixel only, differentlight emitting layers each corresponding to one of R (red), G (green),and B (blue) colors are formed in this embodiment mode. The luminescencein all the light emitting layers may be either luminescence that isgenerated when an excited single state returns to a ground state(fluorescence) or luminescence that is generated when an excited tripletstate returns to a ground state (phosphorescence). The luminescence inone color light emitting layer may be fluorescence (or phosphorescence)while the luminescence in other two color light emitting layers may bephosphorescence (or fluorescence). The luminescence in R light emittinglayer may be phosphorescence and the luminescence in G and B lightemitting layers may be fluorescence. Specifically, the light emittinglayer 119 may have a laminated structure of a hole injection layerformed of copper phthalocyanine (CuPc) with a thickness of 20 nm and alight emitting layer formed of tris-8-quinolinolato aluminum complex(Alq₃) with a thickness of 70 nm. Light emitting color can be controlledby adding to Alq₃ fluorescent pigment such as quinacridone, perylene, orDCM1.

However, the aforementioned material is one example of the organic lightemitting materials used as a light emitting layer, and the invention isnot limited to this at all. A light emitting layer (layer fortransporting carriers to emit light) may be formed by appropriatelycombining a light emitting layer, an electron transporting layer or anelectron injection layer. For example, a low molecular weight organiclight emitting material is used as a light emitting layer in thisembodiment mode, though a medium molecular weight organic light emittingmaterial or a high molecular weight organic light emitting material mayalso be employed. Note that in this specification, a medium molecularweight organic light emitting material means an organic light emittingmaterial that does not have sublimation properties and that has amolecularity of 20 or less, or a length of chained molecules of 10 μm orless. As an example of a light emitting layer using a high molecularweight organic light emitting material, a polythiophene (PEDOT) filmwith a thickness of 20 nm is formed by spin coating as a hole injectionlayer, and a paraphenylene vinylene (PPV) film with a thickness of about100 nm is formed thereon as a light emitting layer. It should be notedthat if π conjugated system polymer of PPV is used, the light emittingwavelengths from red color to blue color can be selected. Moreover, aninorganic material such as silicon carbide can also be used as anelectron transporting layer and an electron injection layer. Knownmaterials can be used as these organic light emitting materials andinorganic materials.

Subsequently, a second electrode 120 formed of a conductive film isprovided on the light emitting layer 119. Since the first electrodefunctions as an anode whereas the second electrode functions as acathode in this embodiment mode, the second electrode 120 may be formedof a material having a low work function (Al, Ag, Li, Ca, or an alloy ofthese elements such as MgAg, MgIn, AlLi, CaF₂, or CaN). This embodimentmode adopts a structure in which the second electrode 120 functions as acathode and light is extracted from the first electrode 113 side thatfunctions as an anode. Therefore, the second electrode 120 is preferablyformed by using a metal film (with a thickness of 50 to 200 nm) formedof Al, Ag, Li, Ca, or an alloy of these elements such as MgAg, MgIn, orAlLi. However, the invention is not limited to this structure, and it isalso possible to adopt a structure in which an N-channel TFT is used asa TFT in a pixel portion, and the first electrode 113 functions as acathode whereas the second electrode 120 functions as an anode.

It is effective to provide a passivation film 121 so as to cover thesecond electrode 120. Used as the passivation film 121 is a single layeror a laminated layer of an insulating film formed of silicon nitride,silicon oxide, silicon oxynitride (SiON), silicon nitride oxide (SiNO),aluminum nitride (AlN), aluminum oxynitride (AlON), aluminum nitrideoxide (AlNO) that contains more nitrogen than oxygen, aluminum oxide,diamond like carbon (DLC), or a carbon film containing nitrogen (CN). Itis also possible to use a material that has a backbone structureobtained by binding silicon (Si) to oxygen (O) and has at least ahydrogen substituent, or a material that has one or more substituentsselected from fluorine, an alkyl group, and aromatic hydrocarbon.

The passivation film 121 is preferably formed of a film having excellentcoverage, and a carbon film, in particular a DLC film is employedefficiently. Since a DLC film can be formed at a temperature rangingfrom room temperature to 100° C., it can be easily formed over the lightemitting layer 119 with low heat resistance. A DLC film may be formed byplasma CVD (typically, RF plasma CVD, microwave CVD, electron cyclotronresonance (ECR) CVD, hot-filament CVD or the like), combustion-flame,sputtering, ion beam vapor deposition, laser vapor deposition, and thelike. As for reaction gas to be used for forming a film, hydrogen gasand hydrocarbon gas (for example, CH₄, C₂H₂, C₆H₆ or the like) are used.These gases are ionized by glow discharge, and after being acceleratedin velocity, the resultant ions collides with a cathode that is appliedwith negative self-bias, thereby forming a film. Further, a CN film maybe formed by using C₂H₄ gas and N₂ gas as reaction gas. A DLC film has abeneficial effect of blocking oxygen, and thereby the light emittinglayer 119 can be prevented from being oxidized. Accordingly, the problemin that the light emitting layer 119 is oxidized during a subsequentsealing step can be solved.

Then, a sealing substrate 123 is attached with a sealing member 124 toseal the light emitting element. The sealing substrate 123 is attachedso that the sealing member 124 may cover the edge of the heat resistantplanarized film 109 (doped region 116). The sealing member 124 preventsmoisture from entering, thus degradation of the light emitting elementcan be prevented and reliability of a display device is improved. Notethat a region surrounded by the sealing member 124 is filled with afiller 122 (see FIG. 2B). In this embodiment mode, light is extractedfrom the first electrode 113 side, therefore, the filler 122 is notrequired to transmit light. However, in the case of light beingextracted through the filler 122, the filler 122 is required to transmitlight. Typically, a visible light curable epoxy resin, a UV curableepoxy resin, or a heat curable epoxy resin may be used. Here, a highheat resistant UV epoxy resin (product name: 2500 Clear, manufactured byElectrolite Corporation) is used, which has a refractive index of 1.50,a viscosity of 500 cps, a Shore D hardness of 90, a tensile strength of3000 psi, a Tg point of 150° C., a volume resistivity of 1×10¹⁵ Ω·cm,and a withstand voltage of 450 V/mil. In addition, total transmittancecan be improved by filling a region between a pair of substrates withthe filler 122.

In a display device manufactured in this manner, the heat resistantplanarized film 109, typically an interlayer insulating film of a TFT(used later as a base film of a light emitting element), which has abackbone structure obtained by binding silicon (Si) to oxygen (O), andthe insulating layer (bank) 114 have an edge or an opening portionhaving a tapered shape. In addition, the heat resistant planarized film109 and the insulator (bank) 114 are doped with at least one elementselected from the elements belonging to Group 13 or Group 15 in theperiodic table, which are relatively large in atomic diameter, in orderto generate distortions and modify or densify the surface (includingside walls). Accordingly, moisture and oxygen can be prevented fromentering, leading to improved reliability of the display device.Moreover, when the first electrode 113 is doped with at least oneelement selected from the elements belonging to Group 13 or Group 15 inthe periodic table, physical properties such as resistance can becontrolled.

Embodiment Mode 2

Embodiment Mode 2 is described in detail with reference to FIGS. 3A to3D, FIGS. 4E and 4F, and FIG. 5.

In this embodiment mode, after forming the heat resistant planarizedfilm, the first electrode, and the insulating layer (bank), each of themis doped with at least one element selected from the elements belongingto Group 13 or Group 15 in the periodic table.

As described in Embodiment Mode 1, base films 301 a and 301 b are formedon a substrate 300, and a semiconductor layer 302 including impurityregions 303 and 304 is formed thereon. Conductive layers 306 and 307 asgate electrodes are formed over the semiconductor layer 302 with a gateinsulating film 305 interposed therebetween, and an insulating film 308is formed thereon as a passivation film. Then, a heat resistantplanarized film 309 is formed as an interlayer film (see FIG. 3A). Thesemanufacturing steps are described in detail (materials, formingconditions and the like) in Embodiment Mode 1. In this embodiment mode,the heat resistant planarized film 309 is formed of an insulating filmthat has a backbone structure obtained by binding silicon (Si) to oxygen(O).

In this embodiment mode, a contact hole (opening portion) 330 is formedin the heat resistant planarized film 309 by using a mask formed of aresist, and the heat resistant planarized film at the peripheral edgeportion of the substrate is removed at the same time. Then, the heatresistant planarized film 309 is doped with a gas 315 having at leastone element selected from the elements belonging to Group 13 or Group 15in the periodic table to form a doped region 316 (see FIG. 3B).

The doping may be performed by an ion doping method, a plasma dopingmethod, or an ion implantation method. As the elements belonging toGroup 13 or Group 15 in the periodic table, B, Al, Ga, In, Tl, P, As,Sb, and Bi can be employed, and typically phosphorous (P) and boron (B)are employed. At least one element selected from the elements belongingto Group 13 or Group 15 in the periodic table, which are relativelylarge in atomic diameter, is doped in order to generate distortions andmodify or densify the surface (including side walls), thereby preventingmoisture and oxygen from entering. In addition, the baking effect of thedoping itself allows moisture to be released during the treatment. Atleast one element selected from the elements belonging to Group 13 orGroup 15 in the periodic table, which is included in the densified area,has a concentration of 1×10¹⁸ to 5×10²¹/cm³, and typically 2×10¹⁹ to2×10²¹/cm³. It is to be noted that the tapered shape of the edge allowsthe side surface of the heat resistant planarized film 309 to be dopedeasily.

In the case of, after forming the contact hole 330, an element with aconductivity being doped to the periphery of the contact hole 330, it ispossible not only to densify the periphery of the contact hole 330 butalso to add the element with a conductivity to the semiconductor layer302 under the contact hole 330. In this embodiment mode, thesemiconductor layer 302 having a P-channel impurity region is doped withboron (B) as at least one element selected from the elements belongingto Group 13 or Group 15 in the periodic table, therefore, a high densityimpurity region 331 can be formed in the semiconductor layer 302 in aself-aligned manner. In addition, the heat resistant planarized film 309can be densified to form a high density impurity region by the samestep. Accordingly, reliability of a display device can be improved andelectrical properties can be controlled without increasing the number ofmanufacturing steps. Such steps for controlling an impurityconcentration and forming a desired impurity region can be applied toEmbodiment Modes 1, 3 to 5 and Embodiments 1 to 6.

Next, a wiring 312 is formed, and then a first electrode 313 is formedso as to be connected to the wiring 312 (see FIG. 3C). In thisembodiment mode, TiN, Al, and TiN are laminated so as to have athickness of 100 nm, 350 nm, and 100 nm respectively, and patterned tomake a desired shape, thereby forming the wiring 312. It is to be notedthat TiN is one of the materials having excellent adhesiveness with theheat resistant planarized film.

This embodiment mode adopts a structure in which a light emittingelement is used as a display element and light from the light emittingelement is extracted from the first electrode side, therefore, the firstelectrode transmits light. A transparent conductive film is formed andetched to be a desired shape to form the first electrode 313. As thefirst electrode 313, a transparent conductive film such as ITO, IZO,ITSO, and indium oxide mixed with zinc oxide (ZnO) of 2 to 20% may beemployed. In this embodiment mode, ITSO is used as the first electrode313. Unlike ITO, ITSO is not crystallized even when baked and remains inthe amorphous state. Accordingly, the planarity of ITSO is superior tothat of ITO, and the first electrode using ITSO is not short-circuitedto the cathode easily even when a layer containing an organic compoundis thin. The first electrode 313 may be swabbed by a polyvinyl alcoholbased porous body and polished by CMP so that the surface thereof may beplanarized. In addition, after being polished by CMP, the surface of thefirst electrode 313 may be irradiated with UV rays or treated withoxygen plasma and the like.

In this embodiment mode, after forming the first electrode 313, thefirst electrode 313 and a part of the heat resistant planarized film 309are doped with a gas 325 containing at least one element selected fromthe elements belonging to Group 13 or Group 15 in the periodic table. Asthe elements belonging to Group 13 or Group 15 in the periodic table, B,Al, Ga, In, Tl, P, As, Sb, and Bi can be employed, and typicallyphosphorous (P) and boron (B) are employed. The doping may be carriedout by an ion doping method, a plasma doping method, or an ionimplantation method. In this embodiment mode, the gas 325 containingboron (B) as at least one element selected from the elements belongingto Group 13 or Group 15 in the periodic table is doped to form a dopedregion 317 (see FIG. 3D). According to the invention, in the dopedregion 317 in the first electrode 313, physical properties such asresistance are varied by the doped element having a conductivity. Thus,electrical properties of the electrode can be controlled according tothe invention.

Then, an insulating layer 314 (referred to as a bank, a barrier or thelike) is formed so as to cover the edge of the first electrode 313 andthe wiring 312. As the insulating layer 314, an SOG film (for example, aSiO_(X) film containing an alkyl group) is formed by an applicationmethod so as to have a thickness of 0.8 to 1 μm. Etching may be eitherdry etching or wet etching. Here, the insulating layer 314 is formed bydry etching using a mixed gas of CF₄, O₂ and He. The dry etching isperformed under such conditions as 5 Pa of pressure, 1500 W, 25 sccm ofCF₄, 25 sccm of O₂, and 50 sccm of He. In this dry etching step, theetching rate of the SiOx film containing an alkyl group is in the rangeof 500 to 600 nm/min whereas the etching rate of the ITSO film is 10nm/min or less, thus, they can have sufficiently high etch selectivity.Further, since the wiring 312 is covered with the insulating layer 314formed of the SiOx film containing an alkyl group, a TiN film havingexcellent adhesiveness is the outer surface. The insulating layer 314may be formed of an insulating film that has a backbone structureobtained by binding silicon (Si) to oxygen (O) as well as a filmincluding a single or more kinds of materials having high heatresistance and high planarization rate, such as an inorganic material(silicon oxide, silicon nitride, silicon oxynitride, silicon nitrideoxide and the like), a photosensitive or non-photosensitive organicmaterial (organic resin material) (polyimide, acryl, polyamide,polyimide amide, resist, benzocyclobutene and the like), and a Low kmaterial as a low dielectric constant material. Alternatively, filmsincluding these materials may be laminated to be used as the insulatinglayer 314.

After forming the insulating layer 314, the insulating layer 314 isdoped with at least one element selected from the elements belonging toGroup 13 or Group 15 in the periodic table. As the elements belonging toGroup 13 or Group 15 in the periodic table, B, Al, Ga, In, Tl, P, As,Sb, and Bi can be employed, and typically phosphorous (P) and boron (B)are employed. The doping may be carried out by an ion doping method, aplasma doping method, or an ion implantation method. In this embodimentmode, a gas 335 containing B as at least one element selected from theelements belonging to Group 13 or Group 15 in the periodic table isdoped to form a doped region 318 (see FIG. 4A). According to theinvention, the doped region 318 in the heat resistant planarized filmand the insulator is densified. At least one element selected from theelements belonging to Group 13 or Group 15 in the periodic table, whichare relatively large in atomic diameter, is doped in order to generatedistortions and modify or densify the surface (including side walls),thereby preventing moisture and oxygen from entering. At least oneelement selected from the elements belonging to Group 13 or Group 15 inthe periodic table, which is included in the doped region, has aconcentration of 1×10¹⁸ to 5×10²¹/cm³, and typically 2×10¹⁹ to2×10²¹/cm³. It is to be noted that the tapered shape of the heatresistant planarized film at the peripheral edge portion of thesubstrate allows the side surface of the heat resistant planarized filmto be doped easily.

When doping at least one element selected from the elements belonging toGroup 13 or Group 15 in the periodic table, the doped region 318 in theinsulating layer 314 functioning as a bank is colored in black.Accordingly, the bank can be used as a black matrix. Thus, according tothe invention, the bank can function as a densified barrier againstcontamination as well as a black matrix with low light transmittance,low reflectivity, and improved optical properties. As a result, it ispossible to provide an inexpensive display device with improved yieldand reliability.

Shown in this embodiment mode is an example in which the insulatinglayer functioning as a bank is formed and patterned, and then the firstelectrode and the bank are doped with at least one element selected fromthe elements belonging to Group 13 or Group 15 in the periodic table.However, patterning may be performed after forming the insulatorfunctioning as a bank and doping the whole surface thereof with at leastone element selected from the elements belonging to Group 13 or Group 15in the periodic table to be colored. In this case, the first electrodeis not doped with at least one element selected from the elementsbelonging to Group 13 or Group 15 in the periodic table during thedoping step, therefore, the concentration of an element, the area to bedoped, and the like can be determined arbitrarily, which expands thedesign flexibility.

In order to improve reliability, it is preferable to perform vacuumheating before forming a light emitting layer 319 containing an organiccompound, thereby performing degasification. For example, it ispreferable to perform heat treatment at a temperature of 200 to 300° C.under a reduced pressure atmosphere or an inert atmosphere in order toremove gas contained in the substrate, before evaporating an organiccompound material. Since the interlayer insulating film and the bank areherein formed of a SiOx film having high heat resistance, heat treatmentat a high temperature can be carried out without any problem.Accordingly, heat treatment steps for improving reliability can beperformed sufficiently.

The light emitting layer 319 is formed on the first electrode 313 (dopedregion 317). Specifically, the light emitting layer 319 may have alaminated structure of a hole injection layer formed of copperphthalocyanine (CuPc) with a thickness of 20 nm and a light emittinglayer formed of tris-8-quinolinolato aluminum complex (Alq₃) with athickness of 70 nm. Light emitting color can be controlled by adding toAlq₃ fluorescent pigment such as quinacridone, perylene, or DCM1.

However, the aforementioned material is one example of the organic lightemitting materials used as a light emitting layer, and the invention isnot limited to this at all. A light emitting layer (layer fortransporting carriers to emit light) may be formed by appropriatelycombining a light emitting layer, an electron transporting layer or anelectron injection layer.

Then, a second electrode 320 formed of a conductive film is provided onthe light emitting layer 319. Since the first electrode functions as ananode whereas the second electrode functions as a cathode in thisembodiment mode, the second electrode 320 may be formed of a materialhaving a low work function (Al, Ag, Li, Ca, or an alloy of theseelements such as MgAg, MgIn, AlLi, CaF₂, or CaN). This embodiment modeadopts a structure in which the second electrode 320 functions as acathode and is light is extracted from the first electrode 313 side thatfunctions as an anode. Therefore, the second electrode 320 is preferablyformed by using a metal film (with a thickness of 50 to 200 nm) formedof Al, Ag, Li, Ca, or an alloy of these elements such as MgAg, MgIn, orAlLi. However, the invention is not limited to this structure, and it isalso possible to adopt a structure in which an N-channel TFT is used asa TFT in a pixel portion, and the first electrode 313 functions as acathode whereas the second electrode 320 functions as an anode.

It is effective to provide a passivation film 321 so as to cover thesecond electrode 320. Used as the passivation film 321 is a single layeror a laminated layer of an insulating film formed of silicon nitride,silicon oxide, silicon oxynitride (SiON), silicon nitride oxide (SiNO),aluminum nitride (AlN), aluminum oxynitride (AlON), aluminum nitrideoxide (AlNO) that contains more nitrogen than oxygen, aluminum oxide,diamond like carbon (DLC), or a carbon film containing nitrogen (CN). Itis also possible to use a material that has a backbone structureobtained by binding silicon (Si) to oxygen (O) and has at least ahydrogen substituent, or a material that has one or more substituentsselected from fluorine, an alkyl group, and aromatic hydrocarbon.

Subsequently, a sealing substrate 323 is attached with a sealing member324 to seal the light emitting element. The sealing substrate 323 isattached so that the sealing member 324 may cover the edge of the heatresistant planarized film 309 (doped region 316). The sealing member 324prevents moisture from entering, thus degradation of the light emittingelement can be prevented and reliability of a display device isimproved. Note that a region surrounded by the sealing member 324 isfilled with a filler 322 (see FIG. 4B). In this embodiment mode, lightis extracted from the first electrode 313 side, therefore, the filler322 is not required to transmit light. However, in the case of lightbeing extracted through the filler 322, the filler 322 is required totransmit light. Here, a high heat resistant UV epoxy resin (productname: 2500 Clear, manufactured by Electrolite Corporation) is used,which has a refractive index of 1.50, a viscosity of 500 cps, a Shore Dhardness of 90, a tensile strength of is 3000 psi, a Tg point of 150°C., a volume resistivity of 1×10¹⁵ Ω·cm, and a withstand voltage of 450V/mil. In addition, total transmittance can be improved by filling aregion between a pair of substrates with the filler 322.

In a display device manufactured in this manner, the heat resistantplanarized film 309, typically an interlayer insulating film of a TFT(used later as a base film of a light emitting element), which has abackbone structure obtained by binding silicon (Si) to oxygen (O), andthe insulating layer (bank) 314 have an edge or an opening portionhaving a tapered shape. In addition, the heat resistant planarized film309 and the insulator (bank) 314 are doped with at least one elementselected from the elements belonging to Group 13 or Group 15 in theperiodic table, which are relatively large in atomic diameter, in orderto generate distortions and modify or densify the surface (includingside walls). Accordingly, moisture and oxygen can be prevented fromentering, leading to improved reliability of the display device.Moreover, when the first electrode 313 is doped with at least oneelement selected from the elements belonging to Group 13 or Group 15 inthe periodic table, physical properties such as resistance can becontrolled.

FIG. 5 shows a case in which after the insulating layer (bank) 314 beingformed, it is not doped with at least one element selected from theelements belonging to Group 13 or Group 15 in the periodic table. Inthat case, the insulating layer 314 used as a bank does not include thedoped region 318. However, the heat resistant planarized film 309includes the doped region 316 that is densified, thus moisture or thelike can be prevented from entering. Accordingly, a display device withimproved reliability can be provided.

Embodiment Mode 3

Embodiment Mode 3 is described in detail with reference to FIGS. 6A to6D and FIG. 7.

In this embodiment mode, after forming the first electrode, a part ofthe heat resistant planarized film and the first electrode are dopedwith at least one element selected from the elements belonging to Group13 or Group 15 in the periodic table.

As described in Embodiment Mode 1, base films 601 a and 601 b are formedon a substrate 600, and a semiconductor layer 602 including impurityregions 603 and 604 is formed thereon. Conductive layers 606 and 607 asgate electrodes are formed over the semiconductor layer 602 with a gateinsulating film 605 interposed therebetween, and an insulating film 608is formed as a passivation film. Then, a heat resistant planarized film609 is formed as an interlayer film (see FIG. 6A). In this embodimentmode, the heat resistant planarized film 609 is formed of an insulatingfilm that has a backbone structure obtained by binding silicon (Si) tooxygen (O).

A contact hole (opening portion) 630 is formed in the heat resistantplanarized film 609 by using a mask formed of a resist, and the heatresistant planarized film 609 at the peripheral edge portion of thesubstrate is removed at the same time (see FIG. 6B).

Subsequently, a wiring 612 is formed, and a first electrode 613 isformed so as to be connected to the wiring 612 (see FIG. 6C). In thisembodiment mode, TiN, Al, and TiN are laminated so as to have athickness of 100 nm, 350 nm, and 100 nm respectively, and patterned tomake a desired shape, thereby forming the wiring 612. It is to be notedthat TiN is one of the materials having excellent adhesiveness with theheat resistant planarized film.

This embodiment mode adopts a structure in which a light emittingelement is used as a display element and light from the light emittingelement is extracted from the first electrode side, therefore, the firstelectrode transmits light. A transparent conductive film is formed andetched to be a desired shape to form the first electrode 613. As thefirst electrode 613, a transparent conductive film such as ITO, IZO,ITSO, and indium oxide mixed with zinc oxide (ZnO) of 2 to 20% may beemployed. In this embodiment mode, ITSO is used as the first electrode613. Unlike ITO, ITSO is not crystallized even when baked and remains inthe amorphous state. Accordingly, the planarity of ITSO is superior tothat of ITO, and the first electrode using ITSO is not short-circuitedto the cathode easily even when a layer containing an organic compoundis thin. The first electrode 613 may be swabbed by a polyvinyl alcoholbased porous body and polished by CMP so that the surface thereof may beplanarized. In addition, after being polished by CMP, the surface of thefirst electrode 613 may be irradiated with UV rays or treated withoxygen plasma and the like. These manufacturing steps are described indetail (materials, forming conditions and the like) in Embodiment Mode1.

In this embodiment mode, after forming the first electrode 613, thefirst electrode 613 and a part of the heat resistant planarized film 609are doped with a gas 615 containing at least one element selected fromthe elements belonging to Group 13 or Group 15 in the periodic table. Asthe elements belonging to Group 13 or Group 15 in the periodic table, B,Al, Ga, In, Ti, P, As, Sb, and Bi can be employed, and typicallyphosphorous (P) and boron (B) are employed. The doping may be carriedout by an ion doping method, a plasma doping method, or an ionimplantation method. In this embodiment mode, the gas 615 containingboron (B) as at least one element selected from the elements belongingto Group 13 or Group 15 in the periodic table is doped to form dopedregions 616, 617 (see FIG. 6D). Further, a part of the heat resistantplanarized film 609, which is not covered with the first electrode 613,is doped with at least one element selected from the elements belongingto Group 13 or Group 15 in the periodic table, and densified. Therefore,moisture, gas and the like are prevented from entering and contaminationof a display device is prevented, leading to improved reliability of thedisplay device. According to the invention, in the doped region 617 inthe first electrode 613, physical properties such as resistance can becontrolled.

Then, an insulating layer 614 (referred to as a bank, a barrier or thelike) is formed so as to cover the edge of the first electrode 613 andthe wiring 612. As the insulating layer 614, an SOG film (for example, aSiO_(X) film containing an alkyl group) is formed by an applicationmethod so as to have a thickness of 0.8 to 1 μm. Etching may be eitherdry etching or wet etching. Here, the insulating layer 614 is formed bydry etching using a mixed gas of CF₄, O₂ and He. The dry etching isperformed under such conditions as 5 Pa of pressure, 1500 W, 25 sccm ofCF₄, 25 sccm of O₂, and 50 sccm of He. In this dry etching step, theetching rate of the SiOx film containing an alkyl group is in the rangeof 500 to 600 nm/min whereas the etching rate of the ITSO film is 10nm/min or less, thus, they can have sufficiently high etch selectivity.Further, since the wiring 612 is covered with the insulating layer 614formed of the SiOx film containing an alkyl group, a TiN film havingexcellent adhesiveness is the outer surface. The insulator 614 may beformed of an insulating film that has a backbone structure obtained bybinding silicon (Si) to oxygen (O) as well as a film including a singleor more kinds of materials having high heat resistance and highplanarization rate, such as an inorganic material (silicon oxide,silicon nitride, silicon oxynitride, silicon nitride oxide and thelike), a photosensitive or non-photosensitive organic material (organicresin material) (polyimide, acryl, polyamide, polyimide amide, resist,benzocyclobutene and the like), and a Low k material as a low dielectricconstant material. Alternatively, films including these materials may belaminated to be used as the insulating layer 614.

Although not shown in this embodiment mode, the insulating layer 614 maybe doped with at least one element selected from the elements belongingto Group 13 or Group 15 in the periodic table after the formationthereof. As the elements belonging to Group 13 or Group 15 in theperiodic table, B, Al, Ga, In, Tl, P, As, Sb, and Bi can be employed,and typically phosphorous (P) and boron (B) are employed. The doping maybe carried out by an ion doping method, a plasma doping method, or anion implantation method. It is to be noted that the doping can beperformed more easily when an edge portion has a tapered shape.

When doping at least one element selected from the elements belonging toGroup 13 or Group 15 in the periodic table, the doped region 618 in theinsulating layer 614 functioning as a bank is colored in black.Accordingly, the bank can be used as a black matrix.

Or, patterning may be performed after forming the insulator functioningas a bank and doping the whole surface thereof with at least one elementselected from the elements belonging to Group 13 or Group 15 in theperiodic table to be colored. In this case, the first electrode is notdoped with at least one element selected from the elements belonging toGroup 13 or Group 15 in the periodic table during the doping step,therefore, the concentration of an element, the area to be doped, andthe like can be determined arbitrarily, which expands the designflexibility.

In order to improve reliability, it is preferable to perform vacuumheating before forming a light emitting layer 619 containing an organiccompound, thereby performing degasification. For example, it ispreferable to perform heat treatment at a temperature of 200 to 300° C.under a reduced pressure atmosphere or an inert atmosphere in order toremove gas contained in the substrate, before evaporating an organiccompound material. Since the interlayer insulating film and the bank areherein formed of a SiOx film having high heat resistance, heat treatmentat a high temperature can be carried out without any problem.Accordingly, heat treatment steps for improving reliability can beperformed sufficiently.

The light emitting layer 619 is formed on the first electrode 613 (dopedregion 617). Specifically, the light emitting layer 619 may have alaminated structure of a hole injection layer formed of copperphthalocyanine (CuPc) with a thickness of 20 nm and a light emittinglayer formed of tris-8-quinolinolato aluminum complex (Alq₃) with athickness of 70 nm. Light emitting color can be controlled by adding toAlq₃ fluorescent pigment such as quinacridone, perylene, or DCM1.

However, the aforementioned material is one example of the organic lightemitting materials used as a light emitting layer, and the invention isnot limited to this at all. A light emitting layer (layer fortransporting carriers to emit light) may be formed by appropriatelycombining a light emitting layer, an electron transporting layer or anelectron injection layer.

Then, a second electrode 620 formed of a conductive film is provided onthe light emitting layer 619. Since the first electrode functions as ananode whereas the second electrode functions as a cathode in thisembodiment mode, the second electrode 620 may be formed of a materialhaving a low work function (Al, Ag, Li, Ca, or an alloy of theseelements such as MgAg, MgIn, AlLi, CaF₂, or CaN). This embodiment modeadopts a structure in which the second electrode 620 functions as acathode and light is extracted from the first electrode 613 side thatfunctions as an anode. Therefore, the second electrode 620 is preferablyformed by using a metal film (with a thickness of 50 to 200 nm) formedof Al, Ag, Li, Ca, or an alloy of these elements such as MgAg, MgIn, orAlLi. However, the invention is not limited to this structure, and it isalso possible to adopt a structure in which an N-channel TFT is used asa TFT in a pixel portion, and the first electrode 613 functions as acathode whereas the second electrode 620 functions as an anode.

It is effective to provide a passivation film 621 so as to cover thesecond electrode 620. Used as the passivation film 621 is a single layeror a laminated layer of an insulating film formed of silicon nitride,silicon oxide, silicon oxynitride (SiON), silicon nitride oxide (SiNO),aluminum nitride (AlN), aluminum oxynitride (AlON), aluminum nitrideoxide (AlNO) that contains more nitrogen than oxygen, aluminum oxide,diamond like carbon (DLC), or a carbon film containing nitrogen (CN). Itis also possible to use a material that has a backbone structureobtained by binding silicon (Si) to oxygen (O) and has at least ahydrogen substituent, or a material that has one or more substituentsselected from fluorine, an alkyl group, and aromatic hydrocarbon.

Subsequently, a sealing substrate 623 is attached with a sealing member624 to seal the light emitting element (see FIG. 7). The sealingsubstrate 623 is attached so that the sealing member 624 may cover theedge of the heat resistant planarized film 609 (doped region 616). Thesealing member 624 prevents moisture from entering, thus degradation ofthe light emitting element can be prevented and reliability of a displaydevice is improved. Note that a region surrounded by the sealing member624 is filled with a filler 622. In this embodiment mode, light isextracted from the first electrode 613 side, therefore, the filler 622is not required to transmit light. However, in the case of light beingextracted through the filler 622, the filler 622 is required to transmitlight. Here, a high heat resistant UV epoxy resin (product name: 2500Clear, manufactured by Electrolite Corporation) is used, which has arefractive index of 1.50, a viscosity of 500 cps, a Shore D hardness of90, a tensile strength of 3000 psi, a Tg point of 150° C., a volumeresistivity of 1×10¹⁵ Ω·cm, and a withstand voltage of 450 V/mil. Inaddition, total transmittance can be improved by filling a regionbetween a pair of substrates with the filler 622.

In a display device manufactured in this manner, the heat resistantplanarized film 609 (typically an interlayer insulating film of a TFTand used later as a base film of a light emitting element), which has abackbone structure obtained by binding silicon (Si) to oxygen (O), hasan opening portion or a tapered shape at a peripheral edge portion ofthe substrate. In addition, the heat resistant planarized film 609 isdoped with at least one element selected from the elements belonging toGroup 13 or Group 15 in the periodic table, which are relatively largein atomic diameter, in order to generate distortions and modify ordensify the surface (including side walls). Accordingly, moisture andoxygen can be prevented from entering, leading to improved reliabilityof the display device. Moreover, when the first electrode 613 is dopedwith at least one element selected from the elements belonging to Group13 or Group 15 in the periodic table, physical properties such asresistance can be controlled.

Embodiment Mode 4

Embodiment Mode 4 is described in detail with reference to FIGS. 9A to9D and FIGS. 10E and 10F.

In this embodiment mode, the heat resistant planarized film and the bank(insulating layer) are formed, and then doped with at least one elementselected from the elements belonging to Group 13 or Group 15 in theperiodic table.

As described in Embodiment Mode 1, base films 901 a and 901 b are formedon a substrate 900, and a semiconductor layer 902 including impurityregions 903 and 904 is formed thereon. Conductive layers 906 and 907 asgate electrodes are formed over the semiconductor layer 902 with a gateinsulating film 905 interposed therebetween, and an insulating film 908is formed as a passivation film. Then, a heat resistant planarized film909 is formed as an interlayer film (see FIG. 9A). In this embodimentmode, the heat resistant planarized film 909 is formed of an insulatingfilm that has a backbone structure obtained by binding silicon (Si) tooxygen (O).

A contact hole (opening portion) 930 is formed in the heat resistantplanarized film 909 by using a mask formed of a resist, and the heatresistant planarized film 909 at the peripheral edge portion of thesubstrate is removed at the same time. Then, the heat resistantplanarized film 909 is doped with a gas 915 containing at least oneelement selected from the elements belonging to Group 13 or Group 15 inthe periodic table to form a doped region 916 (see FIG. 9B).

The doping may be performed by an ion doping method, a plasma dopingmethod, or an ion implantation method. As the elements belonging toGroup 13 or Group 15 in the periodic table, B, Al, Ga, In, Tl, P, As,Sb, and Bi can be employed, and typically phosphorous (P) and boron (B)are employed. At least one element selected from the elements belongingto Group 13 or Group 15 in the periodic table, which are relativelylarge in atomic diameter, is doped in order to generate distortions andmodify or densify the surface (including side walls), thereby preventingmoisture and oxygen from entering. At least one element selected fromthe elements belonging to Group 13 or Group 15 in the periodic table,which is included in the densified area (doped region 916), has aconcentration of 1×10¹⁸ to 5×10²¹/cm³, and typically 2×10¹⁹ to2×10²¹/cm³. It is to be noted that the tapered shape of the edge allowsthe side surface of the heat resistant planarized film 909 to be dopedeasily.

Subsequently, a wiring 912 is formed, and a first electrode 913 isformed so as to be connected to the wiring 912 (see FIG. 9C). In thisembodiment mode, TiN, Al, and TiN are laminated so as to have athickness of 100 nm, 350 nm, and 100 nm respectively, and patterned tomake a desired shape, thereby forming the wiring 912. It is to be notedthat TiN is one of the materials having excellent adhesiveness with theheat resistant planarized film.

This embodiment mode adopts a structure in which a light emittingelement is used as a display element and light from the light emittingelement is extracted from the first electrode side, therefore, the firstelectrode transmits light. A transparent conductive film is formed andetched to be a desired shape to form the first electrode 913. As thefirst electrode 913, a transparent conductive film such as ITO, IZO,ITSO, and indium oxide mixed with zinc oxide (ZnO) of 2 to 20% may beemployed. In this embodiment mode, ITSO is used as the first electrode913. Unlike ITO, ITSO is not crystallized even when baked and remains inthe amorphous state. Accordingly, the planarity of ITSO is superior tothat of ITO, and the first electrode using ITSO is not short-circuitedto the cathode easily even when a layer containing an organic compoundis thin. The first electrode 913 may be swabbed by a polyvinyl alcoholbased porous body and polished by CMP so that the surface thereof may beplanarized. In addition, after being polished by CMP, the surface of thefirst electrode 913 may be irradiated with UV rays or treated withoxygen plasma and the like. These manufacturing steps are described indetail (materials, forming conditions and the like) in Embodiment Modes1 and 2.

Then, an insulator 914 (referred to as a bank, a barrier or the like) isformed so as to cover the edge of the first electrode 913 and the wiring912 (see FIG. 9D). As the insulator 914, an SOG film (for example, aSiO_(X) film containing an alkyl group) is formed by an applicationmethod so as to have a thickness of 0.8 to 1 μm. Etching may be eitherdry etching or wet etching. Here, the insulating layer 914 is formed bydry etching using a mixed gas of CF₄, O₂ and He. The dry etching isperformed under such conditions as 5 Pa of pressure, 1500 W, 25 sccm ofCF₄, 25 sccm of O₂, and 50 sccm of He. In this dry etching step, theetching rate of the SiOx film containing an alkyl group is in the rangeof 500 to 600 nm/min whereas the etching rate of the ITSO film is 10nm/min or less, thus, they can have sufficiently high etch selectivity.Further, since the wiring 912 is covered with the insulator 914 formedof the SiOx film containing an alkyl group, a TiN film having excellentadhesiveness is the outer surface. The insulator 914 may be formed of aninsulating film that has a backbone structure obtained by bindingsilicon (Si) to oxygen (O) as well as a film including a single or morekinds of materials having high heat resistance and high planarizationrate, such as an inorganic material (silicon oxide, silicon nitride,silicon oxynitride, silicon nitride oxide and the like), aphotosensitive or non-photosensitive organic material (organic resinmaterial) (polyimide, acryl, polyamide, polyimide amide, resist,benzocyclobutene and the like), and a Low k material as a low dielectricconstant material. Alternatively, films including these materials may belaminated to be used as the insulator 914.

After forming the insulator 914, the first electrode 913 and theinsulator 914 are doped with at least one element selected from theelements belonging to Group 13 or Group 15 in the periodic table. As theelements belonging to Group 13 or Group 15 in the periodic table, B, Al,Ga, In, Tl, P, As, Sb, and Bi can be employed, and typically phosphorous(P) and boron (B) are employed. The doping may be carried out by an iondoping method, a plasma doping method, or an ion implantation method. Inthis embodiment mode, a gas 935 containing boron (B) as at least oneelement selected from the elements belonging to Group 13 or Group 15 inthe periodic table is doped to form is doped regions 917 and 918 (seeFIG. 10A). According to the invention, the doped regions 917 and 918 inthe heat resistant planarized film and the insulator are densified. Atleast one element selected from the elements belonging to Group 13 orGroup 15 in the periodic table, which are relatively large in atomicdiameter, is doped in order to generate distortions and modify ordensify the surface (including side walls), thereby preventing moistureand oxygen from entering. At least one element selected from theelements belonging to Group 13 or Group 15 in the periodic table, whichis included in the doped regions, has a concentration of 1×10¹⁸ to5×10²¹/cm³, and typically 2×10¹⁹ to 2×10²¹/cm³. It is to be noted thatthe tapered shape of the heat resistant planarized film allows the sidesurface to be doped easily. In addition, when the first electrode 913 isalso doped with at least one element selected from the elementsbelonging to Group 13 or Group 15 in the periodic table, physicalproperties such as resistance can be controlled.

When doping at least one element selected from the elements belonging toGroup 13 or Group 15 in the periodic table, the doped region 918 in theinsulator 914 functioning as a bank is colored in black. Accordingly,the bank can be used as a black matrix. Thus, according to theinvention, the bank can function as a densified barrier againstcontamination as well as a black matrix with low light transmittance,low reflectivity, and improved optical properties. As a result, it ispossible to provide an inexpensive display device with improved yieldand reliability.

Shown in this embodiment mode is an example in which the insulatinglayer functioning as a bank is formed and patterned, and then the firstelectrode and the bank are doped with at least one element selected fromthe elements belonging to Group 13 or Group 15 in the periodic table.However, patterning may be performed after forming the insulating layerfunctioning as a bank and doping the whole surface thereof with at leastone element selected from the elements belonging to Group 13 or Group 15in the periodic table to be colored. In this case, the first electrodeis not doped with at least one element selected from the elementsbelonging to Group 13 or Group 15 in the periodic table during thedoping step, therefore, the concentration of an element, the area to bedoped, and the like can be determined arbitrarily, which expands thedesign flexibility.

In order to improve reliability, it is preferable to perform vacuumheating before forming a light emitting layer 919 containing an organiccompound, thereby performing degasification. For example, it ispreferable to perform heat treatment at a temperature of 200 to 300° C.under a reduced pressure atmosphere or an inert atmosphere in order toremove gas contained in the substrate, before evaporating an organiccompound material. Since the interlayer insulating film and the bank areherein formed of a SiOx film having high heat resistance, heat treatmentat a high temperature can be carried out without any problem.Accordingly, heat treatment steps for improving reliability can beperformed sufficiently.

The light emitting layer 919 is formed on the first electrode 913 (dopedregion 917). Specifically, the light emitting layer 919 may have alaminated structure of a hole injection layer formed of copperphthalocyanine (CuPc) with a thickness of 20 nm and a light emittinglayer formed of tris-8-quinolinolato aluminum complex (Alq₃) with athickness of 70 nm. Light emitting color can be controlled by adding toAlq₃ fluorescent pigment such as quinacridone, perylene, or DCM1.

However, the aforementioned material is one example of the organic lightemitting materials used as a light emitting layer, and the invention isnot limited to this at all. A light emitting layer (layer fortransporting carriers to emit light) may be formed by appropriatelycombining a light emitting layer, an electron transporting layer or anelectron injection layer.

Then, a second electrode 920 formed of a conductive film is provided onthe light emitting layer 919. Since the first electrode functions as ananode whereas the second electrode functions as a cathode in thisembodiment mode, the second electrode 920 may be formed of a materialhaving a low work function (Al, Ag, Li, Ca, or an alloy of theseelements such as MgAg, MgIn, AlLi, CaF₂, or CaN). This embodiment modeadopts a structure in which the second electrode 920 functions as acathode and light is extracted from the first electrode 913 side thatfunctions as an anode. Therefore, the second electrode 920 is preferablyformed by using a metal film (with a thickness of 50 to 200 nm) formedof Al, Ag, Li, Ca, or an alloy of these elements such as MgAg, MgIn, orAlLi. However, the invention is not limited to this structure, and it isalso possible to adopt a structure in which an N-channel TFT is used asa TFT in a pixel portion, and the first electrode 913 functions as acathode whereas the second electrode 920 functions as an anode.

It is effective to provide a passivation film 921 so as to cover thesecond electrode 920. Used as the passivation film 921 is a single layeror a laminated layer of an insulating film formed of silicon nitride,silicon oxide, silicon oxynitride (SiON), silicon nitride oxide (SiNO),aluminum nitride (AlN), aluminum oxynitride (AlON), aluminum nitrideoxide (AlNO) that contains more nitrogen than oxygen, aluminum oxide,diamond like carbon (DLC), or a carbon film containing nitrogen (CN). Itis also possible to use a material that has a backbone structureobtained by binding silicon (Si) to oxygen (O) and has at least ahydrogen substituent, or a material that has one or more substituentsselected from fluorine, an alkyl group, and aromatic hydrocarbon.

Subsequently, a sealing substrate 923 is attached with a sealing member924 to seal the light emitting element. The sealing substrate 923 isattached so that the sealing member 924 may cover the edge of the heatresistant planarized film 909 (doped region 916). The sealing member 924prevents moisture from entering, thus degradation of the light emittingelement can be prevented and reliability of a display device isimproved. Note that a region surrounded by the sealing member 924 isfilled with a filler 922 (see FIG. 10B). In this embodiment mode, lightis extracted from the first electrode 913 side, therefore, the filler922 is not required to transmit light. However, in the case of lightbeing extracted through the filler 922, the filler 922 is required totransmit light. Here, a high heat resistant UV epoxy resin (productname: 2500 Clear, manufactured by Electrolite Corporation) is used,which has a refractive index of 1.50, a viscosity of 500 cps, a Shore Dhardness of 90, a tensile strength of 3000 psi, a Tg point of 150° C., avolume resistivity of 1×10¹⁵ Ω·cm, and a withstand voltage of 450 V/mil.In addition, total transmittance can be improved by filling a regionbetween a pair of substrates with the filler 922.

In a display device manufactured in this manner, the heat resistantplanarized film 909 (typically an interlayer insulating film of a TFTand used later as a base film of a light emitting element), which has abackbone structure obtained by binding silicon (Si) to oxygen (O), andthe insulating layer (bank) 914 have an edge or an opening portionhaving a tapered shape. In addition, the heat resistant planarized film909 and the insulator 914 are doped with at least one element selectedfrom the elements belonging to Group 13 or Group 15 in the periodictable, which are relatively large in atomic diameter, in order togenerate distortions and modify or densify the surface (including sidewalls). Accordingly, moisture and oxygen can be prevented from entering,leading to improved reliability of the display device. Moreover, whenthe first electrode 913 is also doped with at least one element selectedfrom the elements belonging to Group 13 or Group 15 in the periodictable, physical properties such as resistance can be controlled.

Embodiment Mode 5

In this embodiment mode, an example of a display device in which thefirst electrode and the wiring are connected in a different manner isdescribed with reference to FIGS. 11A to 11D and FIGS. 12A and 12B.

As described in Embodiment Mode 1, base films 1101 a and 1101 b areformed on a substrate 1100, and a semiconductor layer 1102 includingimpurity regions 1103 and 1104 is formed thereon. Conductive layers 1106and 1107 as gate electrodes are formed over the semiconductor layer 1102with a gate insulating film 1105 interposed therebetween, and aninsulating film 1108 is formed as a passivation film. Then, a heatresistant planarized film 1109 is formed as an interlayer insulatingfilm (see FIG. 11A). These manufacturing steps are described in detail(materials, forming conditions and the like) in Embodiment Mode 1. Inthis embodiment mode, the heat resistant planarized film 1109 is formedof an insulating film that has a backbone structure obtained by bindingsilicon (Si) to oxygen (O).

A contact hole (opening portion) 1130 is formed in the heat resistantplanarized film 1109 by using a mask formed of a resist, and the heatresistant planarized film 1109 at the peripheral edge portion of thesubstrate is removed at the same time (see FIG. 11B). The heat resistantplanarized film 1109 at the peripheral edge portion of the substrate maybe etched so as to have a tapered shape as shown in FIGS. 11A to 11D.

Subsequently, a first electrode 1113 is selectively formed on the heatresistant planarized film 1109. This embodiment mode adopts a structurein which a light emitting element is used as a display element and lightfrom the light emitting element is extracted from the first electrodeside, therefore, the first electrode transmits light. A transparentconductive film is formed and etched to make a desired shape to form thefirst electrode 1113. As the first electrode 1113, a transparentconductive film such as ITO, IZO, ITSO, and indium oxide mixed with zincoxide (ZnO) of 2 to 20% may be employed. In this embodiment mode, ITSOis used as the first electrode 1113. Unlike ITO, ITSO is notcrystallized even when baked and remains in the amorphous state.Accordingly, the planarity of ITSO is superior to that of ITO, and thefirst electrode using ITSO is not short-circuited to the cathode easilyeven when a layer containing an organic compound is thin. The firstelectrode 1113 may be swabbed by a polyvinyl alcohol based porous bodyand polished by CMP so that the surface thereof may be planarized. Inthis embodiment mode, the first electrode can be formed withoutirregularity because it is formed on the heat resistant planarized film1109 having the planarity. Moreover, treatment of the surface such aspolishing can also be performed easily and sufficiently.

After forming the first electrode 1113, the first electrode 1113 and anedge of the heat resistant planarized film 1109 are doped with at leastone element selected from the elements belonging to Group 13 or Group 15in the periodic table. As the elements belonging to Group 13 or Group 15in the periodic table, B, Al, Ga, In, Tl, P, As, Sb, and Bi can beemployed, and typically phosphorous (P) and boron (B) are employed. Thedoping may be carried out by an ion doping method, a plasma dopingmethod, or an ion implantation method. In this embodiment mode, a gas1115 containing B as at least one element selected from the elementsbelonging to Group 13 or Group 15 in the periodic table is doped to formdoped regions 1116 and 1117 (see FIG. 11D). According to the invention,the edge of the heat resistant planarized film 1109 and the doped region1116 at the periphery of the contact hole 1130 are densified. At leastone element selected from the elements belonging to Group 13 or Group 15in the periodic table, which are relatively large in atomic diameter, isdoped to generate distortions and modify or densify the surface(including side walls), and thereby moisture and oxygen can be preventedfrom entering. At least one element selected from the elements belongingto Group 13 or Group 15 in the periodic table, which is included in thedoped regions, has a concentration of 1×10¹⁸ to 5×10²¹/cm³, andtypically 2×10¹⁹ to 2×10²¹/cm³. It is to be noted that the tapered shapeof the heat resistant planarized film allows the side surface thereof tobe doped easily. Moreover, when the first electrode 1113 is doped withat least one element selected from the elements belonging to Group 13 orGroup 15 in the periodic table, physical properties such as resistancecan be controlled.

Subsequently, a wiring 1112 is formed so as to be connected to the firstelectrode 1113 (see FIG. 12A). In this embodiment mode, TiN, Al, and TiNare laminated so as to have a thickness of 100 nm, 350 nm, and 100 nmrespectively, and patterned to make a desired shape, thereby forming thewiring 1112. It is to be noted that TiN is one of the materials havingexcellent adhesiveness with the heat resistant planarized film. Further,in this embodiment mode, the wring 1112 can be etched by using as anetching stopper the first electrode 1113 that has been formedpreviously. Accordingly, an etching stopper film is not required to beformed separately, thus, the number of manufacturing steps can bereduced.

Then, an insulating layer 1114 (referred to as a bank, a barrier or thelike) is formed so as to cover the edge of the first electrode 1113 andthe wiring 1112. As the insulating layer 1114, an SOG film (for example,a SiO_(X) film containing an alkyl group) is formed by an applicationmethod so as to have a thickness of 0.8 to 1 μm. Etching may be eitherdry etching or wet etching. Here, the insulating layer 1114 is formed bydry etching using a mixed gas of CF₄, O₂ and He. The dry etching isperformed under such conditions as 5 Pa of pressure, 1500 W, 25 sccm ofCF₄, 25 sccm of O₂, and 50 sccm of He. In this dry etching step, theetching rate of the SiOx film containing an alkyl group is in the rangeof 500 to 600 nm/min whereas the etching rate of the ITSO film is 10nm/min or less, thus, they can have sufficiently high etch selectivity.Further, since the wiring 1112 is covered with the insulator 1114 formedof the SiOx film containing an alkyl group, a TiN film having excellentadhesiveness is the outer surface. The insulating layer 1114 may beformed of an insulating film that has a backbone structure obtained bybinding silicon (Si) to oxygen (O) as well as a film including a singleor more kinds of materials having high heat resistance and highplanarization rate, such as an inorganic material (silicon oxide,silicon nitride, silicon oxynitride, silicon nitride oxide and thelike), a photosensitive or non-photosensitive organic material (organicresin material) (polyimide, acryl, polyamide, polyimide amide, resist,benzocyclobutene and the like), and a Low k material as a low dielectricconstant material. Alternatively, films including these materials may belaminated to be used as the insulator 1114.

Although not shown in the, after forming the insulating layer 1114, thefirst electrode 1113 and the insulating layer 1114 may be doped with atleast one element selected from the elements belonging to Group 13 orGroup 15 in the periodic table. As the elements belonging to Group 13 orGroup 15 in the periodic table, B, Al, Ga, In, Tl, P, As, Sb, and Bi canbe employed, and typically phosphorous (P) and boron (B) are employed.The doping may be carried out by an ion doping method, a plasma dopingmethod, or an ion implantation method. The doped region of the insulator1114 is densified by the doping step, and the surface (including sidewalls) is modified to prevent contamination such as moisture fromentering.

In addition, by doping at least one element selected from the elementsbelonging to Group 13 or Group 15 in the periodic table, the dopedregion of the insulating layer 1114 functioning as a bank is colored inblack. Therefore, the bank can also be used as a black matrix. Thus,according to the invention, the bank can function as a densified barrieragainst contamination as well as a black matrix with low lighttransmittance, low reflectivity, and improved optical properties. As aresult, it is possible to provide an inexpensive display device withimproved yield and reliability.

The first electrode and the bank may be doped with at least one elementselected from the elements belonging to Group 13 or Group 15 in theperiodic table, after they are formed and patterned. Alternatively,patterning may be performed after forming the insulating layerfunctioning as a bank and doping the whole surface thereof with at leastone element selected from the elements belonging to Group 13 or Group 15in the periodic table to be colored. In this case, the first electrodeis not doped with at least one element selected from the elementsbelonging to Group 13 or Group 15 in the periodic table during thedoping step, therefore, the concentration of an element, the area to bedoped, and the like can be determined arbitrarily, which expands thedesign flexibility.

In order to improve reliability, it is preferable to perform vacuumheating before forming a light emitting layer 1119 (layer containing anorganic compound), thereby performing degasification. For example, it ispreferable to perform heat treatment at a temperature of 200 to 300° C.under a reduced pressure atmosphere or an inert atmosphere in order toremove gas contained in the substrate, before evaporating an organiccompound material. Since the interlayer insulating film and the bank areherein formed of a SiOx film having high heat resistance, heat treatmentat a high temperature can be carried out without any problem.Accordingly, heat treatment steps for improving reliability can beperformed sufficiently.

The light emitting layer 1119 is formed on the first electrode 1113(doped region 1117). Specifically, the light emitting layer 1119 mayhave a laminated structure of a hole injection layer formed of copperphthalocyanine (CuPc) with a thickness of 20 nm and a light emittinglayer formed of tris-8-quinolinolato aluminum complex (Alq₃) with athickness of 70 nm. Light emitting color can be controlled by adding toAlq₃ fluorescent pigment such as quinacridone, perylene, or DCM1.

However, the aforementioned material is one example of the organic lightemitting materials used as a light emitting layer, and the invention isnot limited to this at all. A light emitting layer (layer fortransporting carriers to emit light) may be formed by appropriatelycombining a light emitting layer, an electron transporting layer or anelectron injection layer.

Then, a second electrode 1120 formed of a conductive film is provided onthe light emitting layer 1119. Since the first electrode functions as ananode whereas the second electrode functions as a cathode in thisembodiment mode, the second electrode 1120 may be formed of a materialhaving a low work function (Al, Ag, Li, Ca, or an alloy of theseelements such as MgAg, MgIn, AlLi, CaF₂, or CaN). This embodiment modeadopts a structure in which the second electrode 1120 functions as acathode and light is extracted from the first electrode 1113 side thatfunctions as an anode. Therefore, the second electrode 1120 ispreferably formed by using a metal film (with a thickness of 50 to 200nm) formed of Al, Ag, Li, Ca, or an alloy of these elements such asMgAg, MgIn, or AlLi. However, the invention is not limited to this isstructure, and it is also possible to adopt a structure in which anN-channel TFT is used as a TFT in a pixel portion, and the firstelectrode 1113 functions as a cathode whereas the second electrode 1120functions as an anode.

It is effective to provide a passivation film 1121 so as to cover thesecond electrode 1120. Used as the passivation film 1121 is a singlelayer or a laminated layer of an insulating film formed of siliconnitride, silicon oxide, silicon oxynitride (SiON), silicon nitride oxide(SiNO), aluminum nitride (AlN), aluminum oxynitride (AlON), aluminumnitride oxide (AlNO) that contains more nitrogen than oxygen, aluminumoxide, diamond like carbon (DLC), or a carbon film containing nitrogen(CN). It is also possible to use a material that has a backbonestructure obtained by binding silicon (Si) to oxygen (O) and has atleast a hydrogen substituent, or a material that has one or moresubstituents selected from fluorine, an alkyl group, and aromatichydrocarbon.

Subsequently, a sealing substrate 1123 is attached with a sealing member1124 to seal the light emitting element. The sealing substrate 1123 isattached so that the sealing member 1124 may cover the edge of the heatresistant planarized film 1109 (doped region 1116) (see FIG. 12B). Thesealing member 1124 prevents moisture from entering, thus degradation ofthe light emitting element can be prevented and reliability of a displaydevice is improved. Note that a region surrounded by the sealing member1124 is filled with a filler 1122. In this embodiment mode, light isextracted from the first electrode 1113 side, therefore, the filler 1122is not required to transmit light. However, in the case of light beingextracted through the filler 1122, the filler 1122 is required totransmit light. Here, a high heat resistant UV epoxy resin (productname: 2500 Clear, manufactured by Electrolite Corporation) is used,which has a refractive index of 1.50, a viscosity of 500 cps, a Shore Dhardness of 90, a tensile strength of 3000 psi, a Tg point of 150° C., avolume resistivity of 1×10¹⁵ Ω·cm, and a withstand voltage of 450 V/mil.In addition, total transmittance can be improved by filling a regionbetween a pair of substrates with the filler 1122.

In a display device manufactured in this manner, the heat resistantplanarized film 1109 (typically an interlayer insulating film of a TFTand used later as a base film of a light emitting element), which has abackbone structure obtained by binding silicon (Si) to oxygen (O), hasan edge or an opening portion having a tapered shape. In addition, theheat resistant planarized film 1109 is doped with at least one elementselected from the elements belonging to Group 13 or Group 15 in theperiodic table, which are relatively large in atomic diameter, in orderto generate distortions and modify or densify the surface (includingside walls). Accordingly, moisture and oxygen can be prevented fromentering, leading to improved reliability of the display device.Moreover, when the first electrode 1113 is also doped with at least oneelement selected from the elements belonging to Group 13 or Group 15 inthe periodic table, physical properties such as resistance can becontrolled and emission efficiency, luminance and the like can also beincreased.

Embodiment 1

In this embodiment, manufacturing steps of the display device explainedin Embodiment Modes 1 to 5 are described with reference to FIGS. 1A to1D, FIGS. 2E and 2F, and FIG. 8.

On the substrate 100 formed of glass, a silicon oxynitride film with athickness of 50 nm and a silicon oxynitride film with a thickness of 100nm are formed by plasma CVD to be used as the base film 101.

Then, a semiconductor film is formed on the base film. In thisembodiment, an amorphous silicon film with a thickness of 54 nm isformed by plasma CVD to be used as the semiconductor film. According tothis embodiment, the amorphous silicon film is crystallized by laserirradiation to form a crystallized semiconductor layer. Beforeirradiating the amorphous silicon film with laser light, the amorphoussilicon film is heated in a nitrogen atmosphere at a temperature of 500°C. for one hour so that hydrogen included in the film may be released tolower hydrogen concentration to 1×10²⁰ atoms/cm³ or less.

Laser crystallization is a method for irradiating a semiconductor filmwith laser light. As for the laser, a solid-state laser, a gas laser, ora metal laser of pulse oscillation or continuous wave oscillation ispreferably used. The solid-state laser includes a YAG laser, a YVO₄laser, a YLF laser, a YAIO₃ laser, a glass laser, a ruby laser, analexandrite laser, a Ti:sapphire laser and the like. The gas laserincludes an excimer laser, an Ar laser, a Kr laser, a CO₂ laser and thelike. The metal layer includes a helium cadmium laser.

The crystalline semiconductor film obtained in this manner is doped witha small amount of impurity element (boron or phosphorous) in order tocontrol a threshold voltage of a TFT.

The semiconductor film is patterned by photolithography using the firstphotomask to form the semiconductor layer 102.

The gate insulating film 105 is formed so as to cover the semiconductorlayer 102. In this embodiment, a silicon oxynitride film with athickness of 115 nm is formed by plasma CVD to be used as thesemiconductor layer 102.

Then, the first conductive film with a thickness of 20 to 100 nm and thesecond conductive film with a thickness of 100 to 400 nm are laminatedin this order on the gate insulating film 105 to be used as a gateelectrode. In this embodiment, a tantalum nitride with a thickness of 30nm is formed on the gate insulating film 105 as the first conductivefilm, and a tungsten film with a thickness of 370 nm is formed thereonas the second conductive film.

The second photomask using a resist is formed by photolithography toperform a first etching step for obtaining an electrode and a wiring.The first conductive film and the second conductive film can be etchedso as to have a tapered shape by ICP (Inductively Coupled Plasma)etching when etching conditions (amount of power applied to a coiledelectrode, amount of power applied to an electrode on the substrateside, temperature of the electrode on the substrate side, and the like)are adjusted appropriately. As etching gas, chlorine gas typified byCl₂, BCl₃, SiCl₄, CCl₄ or the like, or fluorinated gas typified by CF₄,SF₆, NF₃ or the like, can be employed appropriately as well as O₂.

Obtained by the first etching step is a conductive layer having a firstshape, which includes a first conductive layer and a second conductivelayer.

Then, a second etching step is performed without removing the mask usinga resist. A W film is selectively etched herein. At this time, thesecond conductive layer is formed by the second etching step. On theother hand, the first conductive layer is hardly etched to form aconductive layer having a second shape. Accordingly, the conductive film106 and the conductive film 107 are obtained. In this embodiment, theconductive layers are formed by dry etching.

After removing the resist mask, a resist mask as a third photomask isformed. Then, in order to form an N-channel TFT that is not shown in thedrawing, a first doping step is performed to dope an impurity elementthat imparts an N-type conductivity (typically, phosphorous (P) orarsenic (As)) to a semiconductor at a low density. The resist maskcovers an area to be used for a P-channel TFT and a periphery of theconductive layers. By the first doping step, through doping is performedthrough an insulating film to form a low density impurity region. Onelight emitting element is driven by a plurality of TFTs, however, in thecase of the light emitting element being driven by P-channel TFTs only,the aforementioned doping step can be omitted.

After removing the resist mask, a resist mask as a fourth photomask isformed. Then, a second doping step is performed in order to dope animpurity element that imparts a P-type conductivity (typically, boron(B)) to a semiconductor at a high density. By the second doping step,through doping is performed through the gate insulating film 105 to formthe high density impurity regions 103 and 104.

Subsequently, a resist mask as a fifth photomask is formed. Then, inorder to form an N-channel TFT that is not shown in the drawing, a thirddoping step is performed to dope an impurity element that imparts anN-type conductivity (typically, P or As) to a semiconductor at a highdensity. The conditions of the third doping step are such that thedosage is in the range of 1×10¹³ to 5×10¹⁵/cm² and the acceleratingvoltage is in the range of 60 to 100 keV. The resist mask covers an areato be used for a P-channel TFT and a periphery of the conductive layers.By the third doping step, through doping is performed through the gateinsulating film 105 to form an N-type high density impurity region.

In this manner, an impurity region is formed in each semiconductorlayer.

After removing the resist mask, the insulating film 108 containinghydrogen is formed as a passivation film. In this embodiment, a siliconnitride film is formed by sputtering. The insulating film 108 maycontain Ar, and in this embodiment, the concentration of Ar contained inthe film is in the range of approximately 5×10¹⁸ to 5×10²⁰ atoms/cm³.

Furthermore, the semiconductor layer is hydrogenated. In thisembodiment, a heat treatment is carried out in a nitrogen atmosphere ata temperature of 410° C. for one hour to hydrogenate the semiconductorlayer.

Then, the heat resistant planarized film 109 is formed as an interlayerinsulating film. As the heat resistant planarized film 109, aninsulating film that has a is backbone structure obtained by bindingsilicon (Si) to oxygen (O) is formed by an application method.

Manufacturing steps of the heat resistant planarized film 109 aredescribed in Embodiment Mode 1, and thus are omitted herein.

The heat resistant planarized film 109 is formed in this manner.

The insulating film 111 is formed as a passivation film (see FIG. 1A).In this embodiment, a silicon nitride oxide (SiNO) film is formed byplasma CVD so as to have a thickness of 100 nm. When patterning thewiring 112 (used as a drain electrode or a source electrode) insubsequent steps, the insulating film 111 can be used as an etchingstopper film for protecting the heat resistant planarized film 109 thatfunctions as an interlayer insulating film.

The heat resistant planarized film 109 at the peripheral edge portion ofthe substrate is removed simultaneously with the formation of thecontact hole 130 in the heat resistant planarized film 109 with the useof a resist mask. Etching (wet etching or dry etching) is performedherein under the conditions that high etch selectivity is securedrelative to the insulating film 105. In this embodiment, CF₄, O₂, He,and Ar are used. Dry etching is performed by setting the flow of CF₄ at380 sccm; O₂, 290 sccm; He, 500 sccm; Ar, 500 sccm; RF power, 3000 W;and pressure, 25 Pa.

Note that, the etching time may be increased at the rate ofapproximately 10 to 20% for etching the gate insulating film 105 withoutleaving a residue on its surface. In addition, the tapered shape may beobtained by performing the second dry etching with the use of CF₄, O₂,and He by setting the flow of CF₄ at 550 sccm; O₂, 450 sccm; He, 350sccm; RF power, 3000 W; and pressure, 25 Pa. A taper angle θ at the edgeof the heat resistant planarized film 109 is desirably in the rangebetween 30 to 75°.

The gate insulating film 105 is etched to form an opening portion thatextends to a source region or a drain region. In this embodiment, theheat resistant planarized film 109 is etched, and then, the gateinsulating film 105 is etched by using the etched heat resistantplanarized film 109 as a mask to form the opening portion. CHF₃ and Arare used as etching gas for etching the gate insulating film 105. It isto be noted that the etching time may be increased at the rate ofapproximately 10 to 20% for etching the gate insulating film 105 withoutleaving a residue on its surface. Through these manufacturing steps, thecontact hole 130 is formed (see FIG. 1B).

A metal film is formed and etched to form the wiring 112 electricallyconnected to each impurity region (see FIG. 1C). In this embodiment,TiN, Al, and TiN are laminated so as to have a thickness of 100 nm, 350nm, and 100 nm respectively, and patterned to make a desired shape,thereby forming the wiring 112. It is to be noted that TiN is one of thematerials having excellent adhesiveness with the heat resistantplanarized film. Further, in order to be connected to the source regionor the drain region of the TFT, TiN preferably contains N at aconcentration of less than 44%.

Etching is carried out by ICP (Inductively Coupled Plasma) using BCl₃and Cl₂. Etching conditions are such that the amount of power applied toa coiled electrode is 450 W; the amount of power applied to an electrodeon the substrate side is 100 W; and pressure is 1.9 Pa.

Through the aforementioned steps, an active matrix substrate including aTFT is completed.

Subsequently, the first electrode (also called a pixel electrode) 113 isformed so as to be connected to the wiring 112.

Since this embodiment adopts a structure in which a light emittingelement is used as a display element and light from the light emittingelement is extracted from the first electrode 113 side, the firstelectrode 113 transmits light. In this embodiment, ITSO is used for thefirst electrode 113. The ITSO is formed by sputtering using as a targetITO that contains 2 to 10% of silicon oxide. The first electrode 113 maybe swabbed by a polyvinyl alcohol based porous body and polished by CMPso that the surface thereof may be planarized.

Then, the insulator 114 (referred to as a bank, a barrier or the like)is formed so as to cover the edge of the first electrode 113 and thewiring 112 (see FIG. 1D). As the insulator 114, an SOG film (forexample, a SiO_(X) film containing an alkyl group) is formed by anapplication method so as to have a thickness of 0.8 to 1 μm. Theinsulator 114 is formed by dry etching using a mixed gas of CF₄, O₂ andHe. The dry etching is performed under such conditions as 5 Pa ofpressure, 1500 W, 25 sccm of CF₄, 25 sccm of O₂, and 50 sccm of He.Since the wiring 112 is covered with the insulator 114 formed of theSiOx film containing an alkyl group, a TiN film having excellentadhesiveness is the outer surface.

According to the invention, the edge of the heat resistant planarizedfilm 109, the first electrode 113, and the insulator 114 are doped withat least one element selected from the elements belonging to Group 13 orGroup 15 in the periodic table. As the elements belonging to Group 13 orGroup 15 in the periodic table, B, Al, Ga, In, Tl, P, As, Sb, and Bi canbe employed, and typically phosphorous (P) and boron (B) are employed.The doping may be carried out by an ion doping method, a plasma dopingmethod, or an ion implantation method. In this embodiment, the gas 125containing P as at least one element selected from the elementsbelonging to Group 13 or Group 15 in the periodic table is doped to formthe doped regions 116, 117, and 118 (see FIG. 2A). The doping may becarried out at an energy of 1 to 150 kV, and more preferably at anenergy of 50 to 80 kV, and at a dosage of 1×10¹⁴/cm² or more, and morepreferably at a dosage of 1×10¹⁵ to 1×10¹⁶/cm². In this embodiment, thedoping is performed at a dosage of 1×10¹⁶/cm². In a case thatphosphorous (P) is doped to the surface of the heat resistant planarizedfilm or insulating layer, phosphorous exists up to about 5000 Å in thedepth direction from the surface to which phosphorous is added. In acase that boron (B) is doped, boron exists up to about 8000 Å in thedepth direction from the surface to which boron is added.

The amount of moisture in a silicon oxide (SiOx) film containing analkyl group that is used for a heat resistant planarized film and a bankis measured by TDS (Thermal Desorption Spectroscopy) analysis. The TDSanalysis is a spectroscopy for measurement of a gas molecule that isreleased from the sample at each temperature when heating the sample tobe measured. Used as the sample is a film obtained by applying theinvention to a sample formed by patterning a silicon oxide (SiOx) filmcontaining an alkyl group with a resist and removing the resist with aresist stripper. As a comparative example, a film to which the inventionis not applied is employed. The resist stripper used here contains as acomposition 2-aminoethanol HOC₂H₄NH₂ (30 wt %) and glycol etherR—(OCH₂)₂OH (70 wt %). The film to which the invention is applied isdoped with P and B at a dosage of 1×10¹⁶/cm² as at least one elementselected from the elements belonging to Group 13 or Group 15 in theperiodic table.

The measurement result is shown in FIG. 27. White triangular dots markthe P-doped sample to which the invention is applied, white square dotsmark the B-doped sample to which the invention is applied, and whitecircular dots mark the sample to which the invention is not applied as acomparative example. The amount of moisture is measured based on theincreasing and decreasing current values. It is considered that themoisture detected at a temperature of about 80 to 100° C. is the oneevaporated from within or the surface of the film, and the moisturedetected at a temperature of about 250° C. is the one generated fromwithin the film by thermal decomposition of the film. FIG. 27 shows thatat a temperature of about 80 to 100° C. and 250° C., the amount ofmoisture is increased in the comparative example to which the inventionis not applied, while it is decreased significantly in the film to whichthe invention is applied.

As another method for verifying the effect of densification of the filmaccording to the invention, the amount of moisture included in the filmis measured by secondary ion mass spectroscopy (SIMS). As samples, twosilicon oxide (SiOx) films containing an alkyl group are formed andbaked at a temperature of 270° C. for one hour, then, immersed in heavywater at a temperature of 65° C. for one hour One of the films to whichthe invention is applied is measured as well as the other film to whichthe invention is not applied as a comparative example. The film to whichthe invention is applied is doped with P at a dosage of 1×10¹⁶/cm² afterit being baked.

The measurement result is shown in FIG. 28. The abscissa represents thedepth from the sample surface, and the left side represents the film asthe sample whereas the right side represents the substrate. A dottedline at the vicinity of 630 nm depth is a boundary between the film asthe sample and a substrate. Note that the substrate is formed of glass.Black circular dots mark the sample to which the invention is appliedwhile white circular dots mark the sample to which the invention is notapplied as a comparative example. The film to which the invention is notapplied as a comparative example has a peak of deuterium at the vicinityof 700 nm depth in a substrate area. That is, heavy water penetratesinto the film as a comparative example and deuterium extends to theboundary between the substrate and the film. On the other hand,deuterium is not detected in the boundary in the sample to which theinvention is applied, which shows that heavy water does not penetrateinto the film to which the invention is applied.

The aforementioned measurement results verify that the film to which theinvention is applied is densified and improved in quality when dopedwith P or B. The film to which the invention is applied has a low waterpermeability and can prevent moisture or the like from entering. Thus,according to the invention, degradation of a display element can beprevented, leading to further improved reliability of a display device.

Furthermore, the sheet resistance of the first electrode is measured inorder to check changes in electrical properties of the first electrodeaccording to the invention. Two ITSO films are used as samples, and theinvention is applied to one of the films but not applied to the otherfilm. The film to which the invention is applied is doped with P at avoltage of 50 kV and B at a voltage of 80 kV, each of which correspondsto at least one element selected form the elements belonging to Group 13or Group 15 in the periodic table.

The measurement result is shown in FIG. 24. White triangular dots markthe P-doped sample to which the invention is applied, white square dotsmark the B-doped sample to which the invention is applied, and whitecircular dots mark the sample to which the invention is not applied as acomparative example. The film doped with at least one element selectedfrom the elements belonging to Group 13 or Group 15 in the periodictable changes in sheet resistance as compared to the film that is notdoped with at least one element selected from the elements belonging toGroup 13 or Group 15 in the periodic table. In both the films doped withP and B, relative to the comparative example, variation in sheetresistance is increased as the dosage in doping is increased.

The aforementioned measurement result verifies that the first electrodechanges in electrical properties when doped with an element having aconductivity. Thus, according to the invention, electrical properties ofan electrode can be controlled to manufacture a display device havingincreased emission efficiency and luminance.

According to the invention, the doped regions 116 and 118 in the heatresistant planarized film and the insulator are densified. In addition,electrical properties such as resistance can be controlled in the dopedregion 117 in the first electrode. At least one element selected fromthe elements belonging to Group 13 or Group 15 in the periodic table,which are relatively large in atomic diameter, is doped in order togenerate distortions and modify or densify the surface (including sidewalls), thereby preventing moisture and oxygen from entering. Inaddition, the baking effect of the doping itself allows moisture to bereleased during the treatment. At least one element selected from theelements belonging to Group 13 or Group 15 in the periodic table, whichis included in the doped regions, has a concentration of 1×10¹⁸ to5×10²¹/cm³, and typically 2×10¹⁹ to 2×10²¹/cm³. It is to be noted thatthe tapered shape of the edge allows the side surface to be dopedeasily.

In this embodiment, in order to improve reliability, vacuum heating isperformed before forming the light emitting layer 119 containing anorganic compound, thereby performing degasification. Heat treatment isperformed at a temperature of 200 to 300° C. under a reduced pressureatmosphere or an inert atmosphere in order to remove gas contained inthe substrate, before evaporating an organic compound material. Sincethe interlayer insulating film and the bank are formed of a SiOx filmhaving high heat resistance in this embodiment, heat treatment at a hightemperature can be carried out without any problem. Accordingly, heattreatment steps for improving reliability can be performed sufficiently.

The light emitting layer 119 is formed on the first electrode 113 (dopedregion 117). Since the first electrode 113 functions as an anode in thisembodiment, the light emitting layer 119 has a laminated structure of ahole injection layer formed of copper phthalocyanine (CuPc) with athickness of 20 nm and a light emitting layer formed oftris-8-quinolinolato aluminum complex (Alq₃) with a thickness of 70 nm.Light emitting color can be controlled by adding to Alq₃ fluorescentpigment such as quinacridone, perylene, or DCM1.

Subsequently, the second electrode 120 formed of a conductive film isprovided on the light emitting layer 119. Since the first electrodefunctions as an anode whereas the second electrode functions as acathode in this embodiment, the second electrode 120 may be formed of amaterial having a low work function (Al, Ag, Li, Ca, or an alloy ofthese elements such as MgAg, MgIn, AlLi, CaF₂, or CaN). This embodimentadopts a structure in which the second electrode 120 functions as acathode and light is extracted from the first electrode 113 side thatfunctions as an anode. Therefore, the second electrode 120 is preferablyformed by using a metal film (with a thickness of 50 to 200 nm) formedof Al, Ag, Li, Ca, or an alloy of these elements such as MgAg, MgIn, orAlLi.

In this embodiment, the passivation film 121 is provided so as to coverthe second electrode 120. According to this embodiment, a siliconnitride film is formed by using a disk-shaped target formed of siliconin a deposition chamber including a nitrogen atmosphere or a nitrogenand argon atmosphere.

Then, the sealing substrate 123 is attached with the sealing member 124to seal the light emitting element. The sealing substrate 123 isattached so that the sealing member 124 may cover the edge of the heatresistant planarized film 109 (doped region 116 densified by doping).The sealing member 124 prevents moisture from entering, thus degradationof the light emitting element can be prevented and reliability of adisplay device is improved. Note that a region surrounded by the sealingmember 124 is filled with the filler 122 (see FIG. 2B). In thisembodiment, light is extracted from the first electrode 113 side,therefore, the filler 122 is not required to transmit light. However, inthe case of light being extracted through the filler 122, the filler 122is required to transmit light. Typically, a visible light curable epoxyresin, a UV curable epoxy resin, or a heat curable epoxy resin may beused. Here, a high heat resistant UV epoxy resin (product name: 2500Clear, manufactured by Electrolite Corporation) is used, which has arefractive index of 1.50, a viscosity of 500 cps, a Shore D hardness of90, a tensile strength of 3000 psi, a Tg point of 150° C., a volumeresistivity of 1×10¹⁵ Ω·cm, and a withstand voltage of 450 V/mil. Inaddition, total transmittance can be improved by filling a regionbetween a pair of substrates with the filler 122.

FIG. 8 shows an example in which the edge of the display device iscovered with an impermeable protective film. The portions other than theedge are the same as the ones described in this embodiment withreference to FIG. 2B, therefore, the descriptions thereof are omittedherein.

In FIG. 8, reference numeral 800 denotes a TFT, 817 denotes a firstelectrode doped with at least one element selected from the elementsbelonging to Group 13 or Group 15 in the periodic table, 819 denotes alight emitting layer, 820 denotes a second electrode, 821 denotes apassivation film, 822 denotes a filler, 823 denotes a sealing substrate,and 824 denotes a sealing member. An impermeable protective film 830 isformed so as to cover the edge of the doped region 116 in the heatresistant planarized film, which is densified by doping at least oneelement selected from the elements belonging to Group 13 or Group 15 inthe periodic table. In this embodiment, the impermeable protective film830 is formed of a metal layer, and may be formed simultaneously withthe formation of a source electrode or a drain electrode, or may bepatterned to be formed separately.

In the case of using a metal layer, however, a lead wiring connected toa terminal electrode is not covered with the impermeable protective film830. At that time, the edge portion of the substrate may be covered withthe lead wiring.

The impermeable protective film 830 may be formed of one or more kindsof films selected from a conductive thin film and an insulating thinfilm. Used as a conductive thin film may be a film formed of one or morekinds of elements selected from Al, Ti, Mo, W, and Si. Used as aninsulating thin film may be a film formed of one or more kinds ofelements selected from silicon nitride, silicon oxide, silicon nitrideoxide, aluminum nitride, aluminum oxynitride, aluminum nitride oxide,aluminum oxide, diamond like carbon (DLC), and a carbon film containingnitrogen (CN).

When the impermeable protective film 830 covers a side surface of theedge of the heat resistant planarized film, excellent step coverage canbe provided because the edge has a tapered shape. In addition, thesurface of the heat resistant planarized film is doped with at least oneelement selected from the elements belonging to Group 13 or Group 15 inthe periodic table and a densified region 816 is formed, therefore, thesurface exhibits excellent adhesiveness with the metal layer.

According to this embodiment, the impermeable protective film covers theside surface of the edge that is doped with at least one elementselected from the elements belonging to Group 13 or Group 15 in theperiodic table and that has a tapered shape. As a result, moisture orthe like can be prevented from entering.

Further, the embodiment shown in FIG. 8 can be implemented incombination with Embodiment Modes 1 to 5.

A display device manufactured according to this embodiment is describedin more detail with reference to FIGS. 17 and 20.

FIG. 20 is a schematic top plan view of a display device of theinvention. Reference numeral 1500 denotes an element substrate, 1501denotes a source line driver circuit, 1502 and 1503 denote gate linedriver circuits, 1504 denotes a sealing substrate, 1505 denotes asealing member, 1506 denotes a pixel portion, 1507 denotes a scan line,1508 denotes a signal line, 1509 denotes an FPC, 1510, 1511, and 1512denote wirings, and 1520 denotes a protective circuit. FIG. 17 is across sectional view obtained by cutting along a line B-B′ in FIG. 20.Reference numeral 1700 denotes an element substrate, 1701, 1702, and1703 denote TFTs, 1704 denotes a first electrode, 1705 denotes a lightemitting layer, 1706 denotes a second electrode, 1707 denotes apassivation film, 1708 denotes a filler, 1709 denotes a sealing member,1710 denotes a heat resistant planarized film, 1711 denotes a bank, 1712denotes a sealing substrate, 1720 denotes an insulting film, 1730denotes a wiring, 1740 and 1741 denote terminal electrodes, 1742 denotesan anisotropic conductive film, and 1743 denotes an FPC.

FIG. 18 is a cross sectional view showing a lead wiring connected to theaforementioned terminal portion. Reference numeral 1800 denotes anelement substrate, 1803 denotes a TFT, 1804 denotes a first electrode,1805 denotes a light emitting layer, 1806 denotes a second electrode,1807 denotes a passivation film, 1808 denotes a filler, 1809 denotes asealing member, 1810 denotes a heat resistant planarized film, 1811denotes a bank, 1812 denotes a sealing substrate, 1820 denotes aninsulating film, 1830 denotes a lead wiring, 1840 and 1841 denoteterminal electrodes, 1842 denotes an anisotropic conductive film, and1843 denotes an FPC. According to this embodiment, the wiring isprovided so as to cover a densified edge at the peripheral portion andthe terminal portion, therefore, moisture is prevented from enteringexternally and degradation of a display element is inhibited, leading tofurther improved reliability of the display device.

The invention is not limited to such circuit configuration as shown inthis embodiment, and a passive matrix circuit or an active matrixcircuit may also be adopted. Further, an IC chip may be mounted orintegrally formed by COG or TAB so as to function as a peripheral drivercircuit. In addition, the number of gate line driver circuits and sourceline driver circuits is not exclusively limited.

FIG. 20 is a magnified view of the protective circuit 1520. In theprotective circuit of this embodiment, wirings are made in rectangularshape, and capacitance is formed between the wirings to preventelectrostatic discharge, thereby inhibiting defects of the displaydevice, such as electrostatic discharge damage. The protective circuitis not limited to the one shown in this embodiment, and may be formed byappropriately combining a TFT, a capacitor, a diode and the like. Theprotective circuit allows the display device to be further improved inreliability.

Although a light emitting element is used as a display element in thisembodiment, a liquid crystal display element using a liquid crystal mayalso be employed as a display element. Even in the case of a liquidcrystal display element being used, contamination such as moisture canbe blocked by an interlayer insulating film or a bank (spacer) that hasan improved and densified film. Therefore, it is possible not only toprevent contamination from entering from outside the display device butalso to prevent moisture and gas existing within the interlayerinsulating film or the bank from being discharged. As a result,degradation of the display device such as degradation of a liquidcrystal display element due to moisture or the like, and degradation ofwirings or the like can be prevented. It is to be noted that theinterlayer insulating film or the bank colored by doping can be used asa good black matrix as in the case of a light emitting display device.Furthermore, when a pixel electrode is doped with one or more elementsselected from inert elements, O, N, C, Si, and Ge, electrical propertiesof the electrode can be controlled and emission efficiency and luminancecan be improved.

In a display device manufactured in this manner, the heat resistantplanarized film (typically an interlayer insulating film of a TFT andused later as a base film of a light emitting element), which has abackbone structure obtained by binding silicon (Si) to oxygen (O), andthe insulating layer (bank) 114 have an edge or an opening portionhaving a tapered shape. In addition, the heat resistant planarized film109 and the insulating layer (bank) are doped with at least one elementselected from the elements belonging to Group 13 or Group 15 in theperiodic table, which are relatively large in atomic diameter, in orderto generate distortions and modify or densify the surface (includingside walls). Accordingly, moisture and oxygen can be prevented fromentering, leading to improved reliability of the display device.Moreover, when the first electrode is also doped with at least oneelement selected from the elements belonging to Group 13 or Group 15 inthe periodic table, physical properties such as resistance can becontrolled.

Embodiment 2

In this embodiment, the display device shown in Embodiment 1, whichadopts a top emission structure or a dual emission structure, isdescribed with reference to FIGS. 13 and 16.

In FIG. 13, reference numeral 1300 denotes an element substrate, 1301,1302, and 1303 denote TFTs, 1304 denotes a first electrode, 1305 denotesa light emitting layer, 1306 denotes a second electrode, 1307 denotes atransparent conductive film, 1308 denotes a filler, 1309 denotes asealing member, 1310 denotes a heat resistant planarized film, 1311denotes a bank, 1312 denotes a sealing substrate, 1320 denotes aninsulating film, 1330 denotes a wiring, 1340 and 1341 denote terminalelectrodes, 1342 denotes an anisotropic conductive film, and 1343denotes an FPC.

A light emitting display device shown in FIG. 13 is a dual emission typein which light is emitted in both directions shown by arrows. Note thatin this embodiment, a conductive film is formed and etched to make adesired shape, and thereby the first electrode 1304 is formed. As thefirst electrode 1304, a transparent conductive film such as ITO, IZO,ITSO, and indium oxide mixed with zinc oxide (ZnO) of 2 to 20% may beemployed. Alternatively, a titanium nitride film or a titanium film mayalso be used as the first electrode 1304. In that case, after formingthe transparent conductive film, a titanium nitride film or a titaniumfilm is formed to be thin enough to transmit light (preferably about 5to 30 nm). In this embodiment, ITSO is used as the first electrode 1304.

Subsequently, the second electrode 1306 formed of a conductive film isformed on the light emitting layer 1305. The second electrode 1306 maybe formed of a material having a low work function (Al, Ag, Li, Ca, oran alloy of these elements such as MgAg, MgIn, AlLi, CaF₂, or CaN). Inthis embodiment, in order to transmit light, the second electrode 1306is formed of a metal thin film (MgAg with a thickness of 10 nm) and thetransparent conductive film 1307 is formed of ITSO with a thickness of100 nm. The ITSO film is formed by sputtering using as a target indiumtin oxide mixed with 1 to 10% of silicon oxide (SiO₂) and setting theflow of Ar gas at 120 sccm; O₂ gas, 5 sccm; pressure, 0.25 Pa; andpower, 3.2 kW. After forming the ITSO film, a heat treatment is carriedout at a temperature of 200° C. for one hour. As the transparentconductive film 1307, ITO, an alloy of indium oxide and tin oxide, analloy of indium oxide and zinc oxide, zinc oxide, tin oxide, indiumoxide, and the like may be employed.

In the case of adopting the structure shown in FIG. 13, light from thelight emitting element is transmitted and emitted to both the firstelectrode 1304 side and the second electrodes 1306 and 1307 side.

In the display device shown in FIG. 13, the edge of the heat resistantplanarized film 1310, the first electrode 1304 formed of a transparentconductive film, and the bank 1311 are doped with at least one elementselected from the elements belonging to Group 13 or Group 15 in theperiodic table. Manufacturing steps of the display device shown in FIG.13 from the formation of the bank 1311 to the doping of at least oneelement selected from the elements belonging to Group 13 or Group 15 inthe periodic table are the same as those of the display device explainedin Embodiment Mode 1 with reference to FIG. 2A, and they can thus bereferred to.

A light emitting display device shown in FIG. 16 is a top emission type,in which light is emitted to the direction shown by an arrow. In FIG.16, reference numeral 1600 denotes an element substrate, 1601, 1602, and1603 denote TFTs, 1613 denotes a metal film having reflectivity, 1604denotes a first electrode, 1605 denotes a light emitting layer, 1606denotes a second electrode, 1607 denotes a conductive film, 1608 is afiller, 1609 denotes a sealing member, 1610 denotes a heat resistantplanarized film, 1611 denotes a bank, 1612 denotes a sealing substrate,1620 denotes an insulating film, 1630 denotes a wiring, 1640 and 1641denote terminal electrodes, 1642 denotes an anisotropic conductive film,and 1643 denotes an FPC. In this case, the metal film 1613 havingreflectivity is formed under the first electrode 1304 of theaforementioned dual emission display device shown in FIG. 13. The firstelectrode 1604 functioning as an anode is formed on the metal film 1613having reflectivity. The metal film 1613 may be formed of a materialhaving reflectivity such as Ta, W, Ti, Mo, Al, and Cu. In thisembodiment, TiN film is used.

The second electrode 1606 formed of a conductive film is provided on thelight emitting layer 1605. The second electrode 1606 functioning as acathode may be formed of a material having a low work function (Al, Ag,Li, Ca, or an alloy of these elements such as MgAg, MgIn, AlLi, CaF₂, orCaN). In this embodiment, in order to transmit light, the secondelectrode 1606 is formed of a metal thin film (MgAg with a thickness of10 nm) and the transparent conductive film 1607 is formed of ITSO with athickness of 110 nm. As the transparent conductive film 1607, ITO, analloy of indium oxide and tin oxide, an alloy of indium oxide and zincoxide, zinc oxide, tin oxide, indium oxide, and the like may beemployed.

In the display device shown in FIG. 16, the heat resistant planarizedfilm 1610, the first electrode 1604 formed of a transparent conductivefilm, and the bank 1611 are doped with at least one element selectedfrom the elements belonging to Group 13 or Group 15 in the periodictable. Manufacturing steps of the display device shown in FIG. 16 fromthe formation of the bank 1611 to the doping of at least one elementselected from the elements belonging to Group 13 or Group 15 in theperiodic table are the same as those of the display device explained inEmbodiment Mode 4 with reference to FIG. 10A, and they can thus bereferred to.

In the case of adopting the structure shown in FIG. 16, light from thelight emitting element is reflected on the metal film 1613 havingreflectivity and emitted upward through the second electrode 1606, theconductive film 1607 and the like. Therefore, the heat resistantplanarized film 1610 is not required to transmit light, and thus it canbe sufficiently doped with at least one element selected from theelements belonging to Group 13 or Group 15 in the periodic table. Theperiphery of a contact hole for forming the electrode of the TFT canalso be doped with at least one element selected from the elementsbelonging to Group 13 or Group 15 in the periodic table and can bedensified and modified. Accordingly, even when the wiring does not haveexcellent coverage and is broken, moisture can be blocked. Thus,degradation of the display element due to moisture can be prevented,leading to further improved reliability of the display device.

In a display device manufactured in this manner, the heat resistantplanarized film (typically an interlayer insulating film of a TFT andused later as a base film of a light emitting element), which has abackbone structure obtained by binding silicon (Si) to oxygen (O), andthe insulator (bank) have an edge or an opening portion having a taperedshape. In addition, the heat resistant planarized film and theinsulating layer (bank) are doped with at least one element selectedfrom the elements belonging to Group 13 or Group 15 in the periodictable, which are relatively large in atomic diameter, in order togenerate distortions and modify or densify the surface (including sidewalls). Accordingly, moisture and oxygen can be prevented from entering,leading to improved reliability of the display device. Moreover, whenthe first electrode is also doped with at least one element selectedfrom the elements belonging to Group 13 or Group 15 in the periodictable, physical properties such as resistance can be controlled.

Embodiment 3

In this embodiment, an example of an inverted staggered TFT is describedwith reference to FIGS. 14 and 15. The portions other than the TFT arethe same as those described in Embodiment Mode 1 and Embodiment 1 withreference to FIG. 17, therefore, the description thereof is omittedherein. In this embodiment, a passivation film that is formed in FIG. 17is not formed on a heat resistant planarized film, however, thepassivation film may be provided in this embodiment as well.

A TFT shown in FIG. 14 is a channel stop type TFT. Reference numeral1400 denotes an element substrate, and 1401 and 1402 denote TFTs in adriver circuit portion. A gate insulating film 1404, a semiconductorlayer 1405 formed of an amorphous semiconductor film, an n+ layer 1407,and a metal layer 1408 are laminated in this order on a gate electrode1403. A channel stopper 1406 is formed over a channel forming region inthe semiconductor layer 1405. Reference numeral 1411 denotes a sourceelectrode or a drain electrode. Reference numeral 1409 denoted aninsulating film, 1412 denotes a first electrode, 1413 denotes a lightemitting layer, 1414 denotes a second electrode, 1416 denotes apassivation film, 1417 denotes a filler, 1418 denotes a sealing member,1410 denotes a heat resistant planarized film, 1415 denotes a bank, 1419denotes a sealing substrate, 1430 denotes a wiring, 1440 and 1441 denoteterminal electrodes, 1442 denotes an anisotropic conductive film, and1443 denotes an FPC.

A TFT shown in FIG. 15 is a channel etched type TFT. Reference numeral700 denotes an element substrate, and 701 and 702 denote TFTs in adriver circuit portion. A gate insulating film 704, a semiconductorlayer 705 formed of an amorphous semiconductor film, an n+ layer 706,and a metal layer 707 are laminated in this order on a gate electrode703. A channel forming region in the semiconductor layer 705 is etchedslightly. Reference numeral 709 denotes a source electrode or a drainelectrode. Reference numeral 708 denotes an insulating film, 712 denotesa first electrode, 713 denotes a light emitting layer, 714 denotes asecond electrode, 716 denotes a passivation film, 719 denotes a filler,718 denotes a sealing member, 710 denotes a heat resistant planarizedfilm, 715 denotes a bank, 717 denotes a sealing substrate, 730 denotes awiring, 740 and 741 denote terminal electrodes, 742 denotes ananisotropic conductive film, and 743 denotes an FPC.

Instead of the amorphous semiconductor film, a semi-amorphoussemiconductor film (also called a microcrystalline semiconductor film)may be used as well. The semi-amorphous semiconductor is a semiconductorhaving an intermediate structure between amorphous and crystalline(including single crystalline and polycrystalline) structures. Thissemiconductor has a third state that is stable in free energy, andincludes a crystalline region having a short range order and a latticedistortion. The semi-amorphous semiconductor film can be obtained byglow discharge decomposition (plasma CVD) of silicon gas. Typically,SiH₄ is used as a silicon gas, though Si₂H₆, SiH₂Cl₂, SiHCl₃, SiCl₄,SiF₄ or the like may be used as well. The silicon gas may be diluted byadding a single or a plurality of noble gas elements selected from H₂,H₂ and He, Ar, Kr, and Ne. The dilution rate is in the range of 5 to1000 and the pressure is in the range of about 0.1 to 133 Pa. The powersupply frequency is in the range of 1 to 120 MHz, and more preferably inthe range of 13 to 60 MHz. The substrate may be heated at a temperatureof 300° C. or less, and more preferably 100 to 250° C. Among impurityelements that are mainly added during deposition, atmospheric elementssuch as oxygen, nitrogen and carbon desirably have a concentration of1×10²⁰ cm⁻³ or less. In particular, the concentration of oxygen is5×10¹⁹ cm³ or less, and more preferably 1×10¹⁹ cm³ or less. The fieldeffect mobility μ of a TFT using a semi-amorphous semiconductor film asan active layer is in the range of 1 to 10 cm²/Vsec.

The inverted staggered TFTs shown in FIGS. 14 and 15 in this embodimenteach has a semiconductor film formed of an amorphous semiconductor film.Therefore, the TFTs in a pixel portion according to this embodiment areN-channel TFTs, and the first electrodes (pixel electrodes) 1412 and 712function as a cathode while the second electrodes 1414 and 714 functionsas an anode. According to this embodiment, the first electrode and thesecond electrode are formed of ITSO that is a transparent conductivelayer. Adopted in this embodiment is a laminated structure such as anelectron injection layer (BzOs—Li: benzoxazole derivative (BzOs) dopedwith Li), an electron transporting layer (Alq), a light emitting layer(Alq doped with quinacridone derivative (DMQd), a hole transportinglayer (4,4′-bis[N-(1-naphthyl)-N-phenyl-amino]-biphenyl(α-NPD)), a holeinjection layer (molybdenum oxide (MoOx)), the second electrode (ITSO)are laminated in this order over the first electrode (ITSO). Materialsof the electron injection layer, an electron transporting layer, a lightemitting layer, a hole transporting layer, a hole injection layer or thelike for forming the anode, the cathode, and the light emitting layerare not limited to those shown in this embodiment, and may be selectedand combined arbitrarily.

FIG. 29A is a top plan view of a pixel portion of the display deviceaccording to this embodiment, and FIG. 29B is a circuit diagram.Reference numerals 2901 and 2902 denote TFTs, 2903 denotes a lightemitting element, 2904 denotes a capacitor, 2905 denotes a source line,2906 denotes a gate line, 2907 denotes a power source line, and 2908denotes a connection electrode connected a source or drain electrodewith a first electrode (pixel electrode) of the light emitting element2903.

In a display device manufactured in this manner, the heat resistantplanarized film (typically an interlayer insulating film of a TFT andused later as a base film of a light emitting element), which has abackbone structure obtained by binding silicon (Si) to oxygen (O), andthe insulating layer (bank) have an edge or an opening portion having atapered shape. In addition, the heat resistant planarized film and theinsulator (bank) are doped with at least one element selected from theelements belonging to Group 13 or Group 15 in the periodic table, whichare relatively large in atomic diameter, in order to generatedistortions and modify or densify the surface (including side walls).Accordingly, moisture and oxygen can be prevented from entering, leadingto improved reliability of the display device. Moreover, when the firstelectrode is also doped with at least one element selected from theelements belonging to Group 13 or Group 15 in the periodic table,physical properties such as resistance can be controlled.

Embodiment 4

Described in this embodiment is a display device using a black matrixaccording to the invention.

A display device using a light emitting element as a display elementincludes red (R), green (G), and blue (B) pixels for displaying aplurality of colors. A black thin film called a black matrix (alsocalled a light shielding film) is disposed between these pixels. Theblack matrix is provided in order to prevent degradation of TFTs due tolight, prevent light leakage from adjacent electrodes arranged inmatrix, and improve the definition.

Conventionally, used as a black matrix are a Cr black obtained byetching a Cr thin film, a photosensitive resin layer colored with a dyeor a pigment, a film obtained by dispersing a black pigment into apolymer that can be etched, and the like. However, Cr is a toxic metaland has been limited in use in various fields. In addition, a blackmatrix formed of a resin has not exhibited excellent optical propertiesso far, and has many problems. Thus, what is required is a film havinglow reflectivity and transmittance (almost pure black) and beingprocessed (etched) easily.

According to the invention, as described in Embodiment Modes 1 to 4 andEmbodiments 1 to 3 with reference to the drawings, a bank of the displaydevice is doped with at least one element selected from the elementsbelonging to Group 13 or Group 15 in the periodic table. At least oneelement selected from the elements belonging to Group 13 or Group 15 inthe periodic table, which are relatively large in atomic diameter, isdoped in order to generate distortions and modify or densify the surface(including side walls). Accordingly, moisture and oxygen can beprevented from entering, leading to improved reliability of the displaydevice.

According to the invention, when at least one element selected from theelements belonging to Group 13 or Group 15 in the periodic table isdoped to a silicon oxide (SiOx) film containing an alkyl group and afilm containing an organic material such as polyimide and acryl, whichare used for a bank, transmittance of these films changes. Thus,according to the invention, transmittance of a film can be controlledand the film can be colored in black to be used as a black matrix.

Transmittance and reflectivity of a silicon oxide (SiOx) film containingan alkyl group used as a bank are measured. Used as a sample is a filmobtained by applying the invention to a sample formed by patterning asilicon oxide (SiOx) film containing an alkyl group with a resist andremoving the resist with a resist stripper. As a comparative example, afilm to which the invention is not applied is employed. The resiststripper used here contains as a composition 2-aminoethanol HOC₂H₄NH₂(30 wt %) and glycol ether R—(OCH₂)₂OH (70 wt %). The film to which theinvention is applied is doped with P or B at a dosage of 1×10¹⁶/cm² asat least one element selected from the elements belonging to Group 13 orGroup 15 in the periodic table, and two kinds of films are prepared.

The measurement result is shown in FIGS. 23 and 30. In the film to whichthe invention is not applied as a comparative example in FIG. 30, thetransmittance is 90% or more in the visible range of about 400 to 800nm. On the other hand, in the film to which the invention is applied andP or B is doped as at least one element selected from the elementsbelonging to Group 13 or Group 15 in the periodic table, thetransmittance is lowered.

Meanwhile, the measurement result shows that all the samples have a lowreflectivity of 20% or less in the visible range. That is, thereflectivity remains low even when doping at least one element selectedfrom the elements belonging to Group 13 or Group 15 in the periodictable.

The aforementioned measurement results verify that according to theinvention, an organic material is colored and transmittance is lowered,though reflectivity remains low. Therefore, an organic film to which theinvention is applied can be used as a good black matrix. Furthermore,the organic film is harmless and easily processed. Thus, according tothe invention, a bank can function as a densified barrier againstmoisture or the like as well as a black matrix that is easily processedand has improved optical properties.

In the display device described in Embodiment Modes 1 to 4 andEmbodiments 1 to 3 with reference to the drawings, the insulatorfunctioning as a bank is formed and patterned, and then the firstelectrode and the bank are doped with at least one element selected fromthe elements belonging to Group 13 or Group 15 in the periodic table.However, patterning may be performed after forming the insulatorfunctioning as a bank and doping the whole surface thereof with at leastone element selected from the elements belonging to Group 13 or Group 15in the periodic table to be colored. In this case, the first electrodeis not doped with at least one element selected from the elementsbelonging to Group 13 or Group 15 in the periodic table during thedoping step, therefore, the concentration of an element, the area to bedoped, and the like can be determined arbitrarily, which expands thedesign flexibility.

Thus, according to the invention, an inexpensive display device withimproved yield and reliability can be provided while reducing the numberof manufacturing steps.

Embodiment 5

In this embodiment, other display devices according to the invention aredescribed with reference to FIGS. 20, 25, and 26.

FIG. 20 is an example of a top plan view of the display device accordingto the invention. A terminal portion 1509, 1512 and a pixel portion 1506are connected with lead wirings 1510 and 1511 and the like. FIG. 25 isan example of a cross sectional view obtained by cutting along a lineA-A′ of FIG. 20. Reference numeral 3500 denotes an element substrate,3503 denotes a TFT, 3504 denotes a first electrode, 3505 denotes a lightemitting layer, 3506 denotes a second electrode, 3507 denotes apassivation film, 3508 denotes a filler, 3509 denotes a sealing member,3510 denotes a heat resistant planarized film, 3511 denotes a bank, 3512denotes a sealing substrate, and 3520 denotes an insulating film(passivation film). A region shown by dotted lines such as a region 3516is densified by doping of at least one element selected from theelements belonging to Group 13 or Group 15 in the periodic table. Thedensified edge 3516 of the heat resistant planarized film 3510 iscovered with a lead wiring 3530 c, and thereby moisture blocking effectcan be further increased. Three lead wirings 3530 a, 3530 b, and 3530 care shown in the drawing, though the invention is not limited to this.The lead wirings 3530 a, 3530 b, and 3530 c are formed with aninsulating layer 3531 interposed therebetween.

FIG. 26 shows another example of the display device according to theinvention. Reference numeral 3600 denotes an element substrate, 3603denotes a TFT, 3604 denotes a first electrode, 3605 denotes a lightemitting layer, 3606 denotes a second electrode, 3607 denotes apassivation film, 3608 denotes a filler, 3609 denotes a sealing member,3610 denotes a heat resistant planarized film, 3611 denotes a bank, 3612denotes a sealing substrate, and 3620 denotes an insulating film(passivation film). A region shown by dotted lines such as a region 3616is densified by doping of at least one element selected from theelements belonging to Group 13 or Group 15 in the periodic table. Thedensified edge 3616 of the heat resistant planarized film 3610 iscovered with a lead wiring 3630 c, and thereby moisture blocking effectcan be further increased. Three lead wirings 3630 a, 3630 b, and 3630 care shown in the drawing, though the invention is not limited to this.The three lead wirings 3630 a, 3630 b, and 3630 c are formed with thesealing member 3609 interposed therebetween instead of an insulatinglayer.

In the display device shown in FIG. 26, a taper angle of the edge 3616of the heat resistant planarized film 3610 has to be made relativelysmall. This is to avoid the possibility that when a conductive filmfunctioning as a wiring is formed on the edge 3616 with a small taperangle and then patterned by etching, the conductive film may be left onthe tapered edge 3616 as etching residue. The conductive film left onthe edge of the heat resistant planarized film will cause defects suchas a short circuit between wirings.

When an isotropic etching such as wet etching can be carried out, atapered shape can be easily obtained as long as a margin for etching anda certain film thickness can be ensured.

Described in this embodiment is a method for making a desired taperedshape with a relatively small taper angle by anisotropic dry etching.

When forming a mask by photolithography, a slit narrower than aresolution limit of an exposure unit used for exposure is formed at theedge of the photomask so as to make a tapered shape. A mask materialsuch as a resist is not completely exposed in the slit narrower than aresolution limit of an exposure unit, and the mask with a reducedthickness is left after removing the exposed region with a developer.

As described above, a slit or a hole that is narrower than a resolutionlimit of an exposure unit is formed in a photomask. Accordingly, aphotosensitive mask material such as a resist may include anincompletely exposed region between a non-exposed region and acompletely exposed region, and thereby the edge of an etching mask canhave a tapered shape.

When an etching mask with a tapered shape and an object under the maskare both etched by anisotropic etching typified by dry etching, not onlythe object but also the etching mask begins to be etched from a partwith a thinner thickness. When the etching mask is etched anddisappears, the object that is exposed to an etching atmosphere isetched in sequence, and thereby the object with a desired shape can beobtained by reflecting the form of the etching mask more or less.

As a result, with the use of the etching mask having an edge with atapered shape, the object having an edge with the same tapered shape,that is, the edge 3616 with a desired tapered shape of the heatresistant planarized film 3610 in FIG. 26 can be obtained.

The edge 3616 does not include an etching residue of wiring as shown inFIG. 26, therefore, an insulating layer is not required to be providedbetween lead wirings. According to this, manufacturing steps can besimplified, and the insulating layer through which water is easilydispersed can be completely sealed within a display device with asealing member while making an enclosed space. Thus, degradation of adisplay element can be prevented, leading to further improvedreliability of the display device.

Embodiment 6

In this embodiment, other display devices according to the invention aredescribed with reference to FIGS. 19 and 20.

FIG. 20 is an example of a top plan view of the display device accordingto the invention. A cross sectional view as shown in B-B′ of FIG. 20 isshown in FIG. 19. FIG. 19 is a cross sectional view showing a leadwiring portion connected to a terminal portion. Reference numeral 1900denotes an element substrate, 1903 denotes a TFT, 1904 denotes a firstelectrode, 1905 denotes a light emitting layer, 1906 denotes a secondelectrode, 1907 denotes a passivation film, 1908 denotes a filler, 1909denotes a sealing member, 1910 denotes a heat resistant planarized film,1911 denotes a bank, 1912 denotes a sealing substrate, 1920 denotes aninsulating film (passivation film), 1930 denotes a lead wiring, 1940 and1941 denote terminal electrodes, 1942 denotes an anisotropic conductivefilm, and 1943 denotes an FPC. In the display device of this embodiment,densified edges 1916 and 1926 are covered with wirings 1930 and 1933 atthe peripheral portion and the terminal portion. Therefore, moisture canbe prevented from entering and deterioration of the display element canbe inhibited, leading to improved reliability.

In FIG. 19, a contact hole is formed in the heat resistant planarizedfilm 1910 in order to form an electrode 1927 connected to asemiconductor layer, while removing the heat resistant planarized film1910 in the peripheral edge portion of the substrate. At this time, thecontact hole can be etched without irregularity because thesemiconductor layer functions as an etching stopper. However, asemiconductor layer, namely an etching stopper is not formed over asubstrate at the peripheral portion and the terminal portion, thus abase film and a glass substrate are etched. Therefore, the base film orthe glass substrate cannot have high planarization rate and hasirregular surface thereof at the peripheral portion and the terminalportion.

When a wiring is formed over the film with irregularity, a conductivefilm cannot have excellent coverage, which causes defects such as brokenwiring and short circuit. Further, the irregularity causes variations inreflectivity of the wiring, leading to a clouded pattern at theperipheral portion and the terminal portion.

Accordingly, in the display device shown in FIG. 19, layers 1931 and1932 functioning as etching stoppers are formed in the peripheralportion and the edge portion. Each of the etching stopper layers 1931and 1932 is preferably formed of a material having high etch selectivityrelative to a gate insulating film, such as a material used for asemiconductor layer such as silicon or a conductive layer used for agate electrode. When the etching stopper layers 1931 and 1932 are formedof the same material as that used for forming a TFT, they can beobtained in the same step as the formation of the TFT, and thereby themanufacturing steps can be simplified.

In this embodiment, the etching stopper layers 1931 and 1932 are formedof silicon that is the same material as a semiconductor layer. Since theetching stopper layers 1931 and 1932 function as etching stoppers,insulating layers such as the heat resistant planarized film at theterminal portion and the peripheral portion can be etched withoutirregularity. Therefore, the wirings 1930 and 1933 can be formed thereonwith excellent coverage. Electrical property defects and appearancedefects such as a clouded pattern due to variations in reflectivity canthus be solved, leading to improved reliability of the display device.

Since the etching stopper layers 1931 and 1932 are doped with animpurity element such as phosphorous and boron, the display device issurrounded part way by a semiconductor layer with relatively lowresistance, and potentials on the whole substrate can be kept equal.Accordingly, electrostatic discharge damage and plasma damage can alsobe prevented.

Thus, according to the invention, a display device with improvedreliability and yield can be provided.

Embodiment 7

The invention can be applied to various display devices. That is, theinvention can be applied to various electronic appliances using thesedisplay devices for a display portion.

The invention can be applied to electronic appliances such as a videocamera, digital camera, a projector, a head mounted display (goggle typedisplay), a car navigation system, an in-car audio system, a personalcomputer, a game machine, a portable information terminal (mobilecomputer, mobile phone, an electronic book or the like), an imagereproducing device provided with a recording medium (specifically, adevice that can reproduce a recording medium such as a DVD (DigitalVersatile Disc) and that includes a display capable of displaying thereproduced image). Examples of these electronic appliances are shown inFIGS. 21A to 21E.

FIG. 21A illustrates a display device having, for example, a 20 to80-inch large display portion. The display device includes a housing2001, a supporting base 2002, a display portion 2003, speaker portions2004, a video input terminal 2005 and the like. The invention can beapplied to the display portion 2003. In view of the productivity and thecost, such a large display device is preferably formed by using a largesubstrate of a so-called fifth generation (1000×1200 mm), sixthgeneration (1400×1600 mm), or seventh generation (1500×1800 mm) panel.According to the invention, an inexpensive display device with improvedreliability can be provided while reducing the number of manufacturingsteps, even when using such a large substrate.

FIG. 21B illustrates a laptop personal computer that includes a mainbody 2101, a housing 2102, a display portion 2103, a keyboard 2104, anexternal connecting port 2105, a pointing mouse 2106 and the like. Theinvention can be applied to the display portion 2103. According to theinvention, a laptop personal computer that is often used in the open aircan provide a high quality image with improved reliability even whenbeing used in a harsh environment.

FIG. 21C illustrates an image reproducing device provided with arecording medium (specifically, a DVD reproducing device), that includesa main body 2201, a housing 2202, a display portion A2203, a displayportion B2204, a recording medium (such as DVD) reading portion 2205, anoperating key 2206, a speaker portion 2207 and the like. The displayportion A 2203 mainly displays image data whereas the display portionB2204 mainly displays character data. The invention can be applied tothese display portions A2203 and B2204. According to the invention, ahigh quality image can be provided with improved reliability.

FIG. 21D illustrates a mobile phone that includes a main body 2301, anaudio output portion 2302, an audio input portion 2303, a displayportion 2304, operating switches 2305, an antenna 2306 and the like.When the display device according to the invention is applied to thedisplay portion 2304, a mobile phone that is often used in a hot andhumid environment such as in the open air can provide a high qualityimage with improved reliability.

FIG. 21E illustrates a video camera that includes a main body 2401, adisplay portion 2402, a housing 2403, an external connecting port 2404,a remote control receiving portion 2405, an image receiving portion2406, a battery 2407, an audio input portion 2408, operating keys 2409and the like. The invention can be applied to the display portion 2402.When the display device according to the invention is applied to thedisplay portion 2402, a video camera can provide a high quality imagewith improved reliability even when being used in a hot and humidenvironment such as in the open air.

FIG. 22 shows an example of a display portion mounted on an auto car.Although an auto car is taken as an example of a vehicle herein, theinvention is not exclusively limited to this and may be applied to aplane, a train, an electric train or the like. In particular, it isimportant for a display device mounted on an auto car to have highreliability even in a harsh environment (in a hot and humid car).

FIG. 22 illustrates an area around the driver seat. A dashboard 2507includes an audio reproducing device, specifically an in-car audiosystem and a car navigation system. A main body 2505 of the in-car audiosystem includes a display portion 2504 and an operating button 2508. Theinvention is applied to the display portion 2504, leading to highreliability of the in-car audio system.

The invention can also be applied to a display portion 2503 of the carnavigation system and a display portion 2506 for displaying the statusof air conditioning in the car, leading to high reliability of the carnavigation system.

Although the in-car audio system and the car navigation system are shownin this embodiment, the invention can be applied to a display device forother vehicles, and a stationary audio system or navigation system.

As set forth above, the application range of the invention is so widethat the invention can be applied to electronic appliances of allfields.

This application is based on Japanese Patent Application serial no.2003-365229 filed in Japan Patent Office on 24, Oct., 2003, the contentsof which are hereby incorporated by reference.

Although the present invention has been fully described by way ofEmbodiment Modes and Embodiments with reference to the accompanyingdrawings, it is to be understood that various changes and modificationswill be apparent to those skilled in the art. Therefore, unless suchchanges and modifications depart from the scope of the present inventionhereinafter defined, they should be constructed as being includedtherein.

1. A manufacturing method of a display device comprising: forming a thinfilm transistor over a first substrate; forming an interlayer insulatingfilm over the thin film transistor; removing the interlayer insulatingfilm selectively so that at least one opening is formed in theinterlayer insulating film and a side surface of the interlayerinsulating film has a tapered shape at an edge of the first substrate;first doping an impurity element of one conductivity to the openingportion and the side surface of the interlayer insulating film; forminga first electrode electrically connected to the thin film transistorover the interlayer insulating film; forming an insulating layercovering an edge of the first electrode; second doping an impurityelement of one conductivity to the first electrode and the insulatinglayer; forming a layer including an organic compound over the firstelectrode; and forming a second electrode over the layer including anorganic compound, wherein at the first doping step, a high concentrationimpurity region is formed in a semiconductor layer of the thin filmtransistor.
 2. The manufacturing method of a display device, accordingto claim 1, wherein the method further comprises attaching a secondsubstrate to the first substrate with a sealing member surrounding anouter edge of the interlayer insulating film.
 3. The manufacturingmethod of a display device, according to claim 1, wherein the highconcentration impurity region is formed in a source region or a drainregion of the semiconductor layer.
 4. The manufacturing method of adisplay device, according to claim 1, wherein the side surface of theinterlayer insulating film is tapered in the range between 30 and 75°.5. The manufacturing method of a display device, according to claim 1,wherein the impurity element of one conductivity is doped so that adosage thereof is equal in the first electrode and the insulating layer.6. The manufacturing method of a display device, according to claim 1,wherein the impurity element of one conductivity is doped so that theconcentration thereof is in the range of 1×10¹⁸ to 5×10²¹/cm³, andtypically in the range of 2×10¹⁹ to 2×10²¹/cm³.
 7. The manufacturingmethod of a display device, according to claim 1, wherein at least oneelement selected from elements belonging to Group 13 or Group 15 in theperiodic table is doped as the impurity element of one conductivity. 8.The manufacturing method of a display device, according to claim 1,wherein the interlayer insulating film or the insulating layer is formedby an application method using a silicon oxide film including an alkylgroup.
 9. The manufacturing method of a display device, according toclaim 1, wherein the first electrode is formed by sputtering using as atarget indium tin oxide including silicon oxide.
 10. The manufacturingmethod of a display device, according to claim 1, wherein the insulatinglayer is colored to be used as a black matrix.